How to manually install Windows Defender?


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infinity

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Win 11
I just realised it's not available. How do I manually install it?

websiteforstudents.com

How to Exclude Files from Microsoft Defender on Windows 11

Boost your Windows 11 performance by learning how to exclude files from Microsoft Defender. Enhance efficiency while staying cautious about security.
websiteforstudents.com websiteforstudents.com
 

My Computer My Computer

At a glance

Win 11Ryzen 3600GSkill RipJawz 16Gbx2GTX960
OS
Win 11
Computer type
PC/Desktop
CPU
Ryzen 3600
Motherboard
MSI B450 Tomahawk Max
Memory
GSkill RipJawz 16Gbx2
Graphics Card(s)
GTX960
Screen Resolution
2560x1440
Hard Drives
WD750 SSD 1TB
PSU
650w FSP
infinity said:
I just realised it's not available. How do I manually install it?
Click to expand...
Defender should be installed already, it's part of Windows. One reason it could be missing is if you have installed a 3rd-party AV. Doing so will disable Defender. You can't run two AVs at the same time.
 

My Computers My Computers

System One System Two Other systems

  • At a glance

    Windows 11 HomeAMD Athlon Silver 3050U8GBRadeon Graphics
    OS
    Windows 11 Home
    Computer type
    Laptop
    Manufacturer/Model
    Acer Aspire 3 A315-23-R9VY
    CPU
    AMD Athlon Silver 3050U
    Memory
    8GB
    Graphics Card(s)
    Radeon Graphics
    Monitor(s) Displays
    laptop screen
    Screen Resolution
    1366x768 native resolution, up to 2560x1440 with Radeon Virtual Super Resolution
    Hard Drives
    1TB Samsung EVO 870 SSD (from April 2026: 250GB EVO 850)
    Internet Speed
    150 Mbps
    Browser
    Edge, Firefox
    Antivirus
    Defender
    Other Info
    fully 'Windows 11 ready' laptop. Windows 10 C: partition migrated from my old unsupported 'main machine' then upgraded to 11. A test migration ran Insider builds for 2 months. When 11 was released on 5th October 2021 it was re-imaged back to 10 and was offered the upgrade in Windows Update on 20th October. Windows Update offered the 22H2 Feature Update on 20th September 2022. It got the 23H2 Feature Update on 4th November 2023 through Windows Update, 24H2 on 3rd October 2024 through Windows Update by setting the Target Release Version for 24H2, and 25H2 on 30th September 2025 through Windows Update by setting the Target Release Version for 25H2.

    UPDATE - 11 April 2026: due to mechanical deterioration this PC has been retired from active duty. The OS with all software and files has been migrated to my System Seven in 'Other systems' to carry on as my general purpose 'main machine'.

  • At a glance

    Windows 11 ProIntel® Core™ i5-520M8GB(integrated graphics) Intel HD Graphics
    Operating System
    Windows 11 Pro
    Computer type
    Laptop
    Manufacturer/Model
    Dell Latitude E4310
    CPU
    Intel® Core™ i5-520M
    Motherboard
    0T6M8G
    Memory
    8GB
    Graphics card(s)
    (integrated graphics) Intel HD Graphics
    Screen Resolution
    1366x768
    Hard Drives
    500GB Crucial MX500 SSD
    Browser
    Firefox, Edge
    Antivirus
    Defender
    Other Info
    unsupported machine: Legacy bios, MBR, TPM 1.2, upgraded from W10 to W11 using W10/W11 hybrid install media workaround.

    In-place upgrade to 22H2 using ISO and a workaround.
    Feature Update to 23H2 by manually installing the Enablement Package.
    In-place upgrade to 24H2 using hybrid 23H2/24H2 install media.
    Upgraded to 25H2 by Enablement Package.

    Also running Insider Dev, and Canary builds and Windows 10 as native boot .vhdx.
  • My SYSTEM THREE is a Dell Latitude 5410, i7-10610U, 32GB RAM, 512GB NVMe ssd, supported device running Windows 11 Pro.

    My SYSTEM FOUR is a 2-in-1 convertible Lenovo Yoga 11e 20DA, Celeron N2930, 8GB RAM, 256GB ssd. Unsupported device: currently running Win10 Pro, plus Win11 Pro RTM and Insider Dev, Beta, and RP 24H2 as native boot vhdx.

    My SYSTEM FIVE is a Dell Latitude 3190 2-in-1, Pentium Silver N5030, 8GB RAM, 1TB NVMe ssd, supported device running Windows 11 Pro, plus Insider Beta, Dev, and Canary builds (and a few others) as a native boot .vhdx.

    My SYSTEM SIX is a Dell Latitude 5550, Core Ultra 7 165H, 64GB RAM, 1TB NVMe SSD, supported device, Windows 11 Pro 24H2, Hyper-V host machine. Updated to 25H2 on 30th September 2025.

    My SYSTEM SEVEN is a Lenovo Thinkpad T580, Intel Core i7-8650U, 16GB RAM, 512GB NVMe SSD + 2nd 512GB NVMe SSD, a supported device for Windows 11. This is my current general purpose 'main machine'. The installed Windows 11 Home from my System One has been migrated to this machine.
hmm I have not installed a new AV yet though.
 

My Computer My Computer

At a glance

Win 11Ryzen 3600GSkill RipJawz 16Gbx2GTX960
OS
Win 11
Computer type
PC/Desktop
CPU
Ryzen 3600
Motherboard
MSI B450 Tomahawk Max
Memory
GSkill RipJawz 16Gbx2
Graphics Card(s)
GTX960
Screen Resolution
2560x1440
Hard Drives
WD750 SSD 1TB
PSU
650w FSP
Do you have Windows Security showing in the all apps list?
 

My Computers My Computers

System One System Two

  • At a glance

    Win 11 ProAMD Ryzen™ 7 7730U24GB Dual-Channel DDR4 @ 1596MHz (22-22-22-52)512MB ATI AMD Radeon Graphics (ASUStek Comput...
    OS
    Win 11 Pro
    Computer type
    Laptop
    Manufacturer/Model
    ASUS Vivobook
    CPU
    AMD Ryzen™ 7 7730U
    Motherboard
    M1605YA
    Memory
    24GB Dual-Channel DDR4 @ 1596MHz (22-22-22-52)
    Graphics Card(s)
    512MB ATI AMD Radeon Graphics (ASUStek Computer Inc)
    Monitor(s) Displays
    Generic PnP Monitor (1920x1200@60Hz) - P1 PLUS (1920x1080@59Hz)
    Screen Resolution
    1920 X 1200
    Hard Drives
    953GB Western Digital WD
    PSU
    45 Watts
    Mouse
    Lenovo Bluetooth.
    Internet Speed
    500 Mbps
    Browser
    Edge
    Antivirus
    Defender

  • At a glance

    Windows 11AMD Ryzen 7 5800H / 3.2 GHz32 GB DDR4 SDRAM 3200 MHzNVIDIA GeForce RTX 3060 6 GB GDDR6 SDRAM
    Operating System
    Windows 11
    Computer type
    Laptop
    Manufacturer/Model
    ACER NITRO
    CPU
    AMD Ryzen 7 5800H / 3.2 GHz
    Motherboard
    CZ Scala_CAS (FP6)
    Memory
    32 GB DDR4 SDRAM 3200 MHz
    Graphics card(s)
    NVIDIA GeForce RTX 3060 6 GB GDDR6 SDRAM
    Sound Card
    Realtek Audio. NVIDIA High Definition Audio
    Monitor(s) Displays
    15.6" LED backlight 1920 x 1080 (Full HD) 144 Hz
    Screen Resolution
    1920 x 1080 (Full HD)
    Hard Drives
    Samsung 970 Evo Plus 2TB NVMe M.2
    PSU
    180 Watt, 19.5 V
    Mouse
    Lenovo Bluetooth
    Internet Speed
    500 Mbps
    Browser
    Edge
    Antivirus
    Defender
no there isn't.
 

My Computer My Computer

At a glance

Win 11Ryzen 3600GSkill RipJawz 16Gbx2GTX960
OS
Win 11
Computer type
PC/Desktop
CPU
Ryzen 3600
Motherboard
MSI B450 Tomahawk Max
Memory
GSkill RipJawz 16Gbx2
Graphics Card(s)
GTX960
Screen Resolution
2560x1440
Hard Drives
WD750 SSD 1TB
PSU
650w FSP
Unless you have some modified version of Windows, or been using some dodgy scripts to remoove/disable it it is virtually impossible not to have Defender as it is a core application.

Reinstalling Windows from scratch is your only realistic solution.
 

My Computer My Computer

At a glance

Windows 11 Pro + Win11 Canary VM.I9 13th gen i9-13900H 2.60 GHZ16 GB solderedIntegrated Intel Iris XE
OS
Windows 11 Pro + Win11 Canary VM.
Computer type
Laptop
Manufacturer/Model
ASUS Zenbook 14
CPU
I9 13th gen i9-13900H 2.60 GHZ
Motherboard
Yep, Laptop has one.
Memory
16 GB soldered
Graphics Card(s)
Integrated Intel Iris XE
Sound Card
Realtek built in
Monitor(s) Displays
laptop OLED screen
Screen Resolution
2880x1800 touchscreen
Hard Drives
1 TB NVME SSD (only weakness is only one slot)
PSU
Internal + 65W thunderbolt USB4 charger
Case
Yep, got one
Cooling
Stella Artois (UK pint cans - 568 ml) - extra cost.
Keyboard
Built in UK keybd
Mouse
Bluetooth , wireless dongled, wired
Internet Speed
900 mbs (ethernet), wifi 6 typical 350-450 mb/s both up and down
Browser
Edge
Antivirus
Defender
Other Info
TPM 2.0, 2xUSB4 thunderbolt, 1xUsb3 (usb a), 1xUsb-c, hdmi out, 3.5 mm audio out/in combo, ASUS backlit trackpad (inc. switchable number pad)

Macrium Reflect Home V8
Office 365 Family (6 users each 1TB onedrive space)
Hyper-V (a vm runs almost as fast as my older laptop)
I see. in that case I'll just go with a 3ʳᵈ party AV. Is Avast the absolute best compared to all others in detection rate?
 

My Computer My Computer

At a glance

Win 11Ryzen 3600GSkill RipJawz 16Gbx2GTX960
OS
Win 11
Computer type
PC/Desktop
CPU
Ryzen 3600
Motherboard
MSI B450 Tomahawk Max
Memory
GSkill RipJawz 16Gbx2
Graphics Card(s)
GTX960
Screen Resolution
2560x1440
Hard Drives
WD750 SSD 1TB
PSU
650w FSP
infinity said:
Is Avast the absolute best compared to all others in detection rate?
Click to expand...
No, there is no single clear ''best'. Almost all, including Defender, get ranked equally with a top score of straight 6's here:
www.av-test.org

Test antivirus software for Windows 11 - February 2026

The current tests of antivirus software for Windows 11 from February 2026 of AV-TEST, the leading international and independent service provider for antivirus software and malware.
www.av-test.org www.av-test.org
 

My Computers My Computers

System One System Two Other systems

  • At a glance

    Windows 11 HomeAMD Athlon Silver 3050U8GBRadeon Graphics
    OS
    Windows 11 Home
    Computer type
    Laptop
    Manufacturer/Model
    Acer Aspire 3 A315-23-R9VY
    CPU
    AMD Athlon Silver 3050U
    Memory
    8GB
    Graphics Card(s)
    Radeon Graphics
    Monitor(s) Displays
    laptop screen
    Screen Resolution
    1366x768 native resolution, up to 2560x1440 with Radeon Virtual Super Resolution
    Hard Drives
    1TB Samsung EVO 870 SSD (from April 2026: 250GB EVO 850)
    Internet Speed
    150 Mbps
    Browser
    Edge, Firefox
    Antivirus
    Defender
    Other Info
    fully 'Windows 11 ready' laptop. Windows 10 C: partition migrated from my old unsupported 'main machine' then upgraded to 11. A test migration ran Insider builds for 2 months. When 11 was released on 5th October 2021 it was re-imaged back to 10 and was offered the upgrade in Windows Update on 20th October. Windows Update offered the 22H2 Feature Update on 20th September 2022. It got the 23H2 Feature Update on 4th November 2023 through Windows Update, 24H2 on 3rd October 2024 through Windows Update by setting the Target Release Version for 24H2, and 25H2 on 30th September 2025 through Windows Update by setting the Target Release Version for 25H2.

    UPDATE - 11 April 2026: due to mechanical deterioration this PC has been retired from active duty. The OS with all software and files has been migrated to my System Seven in 'Other systems' to carry on as my general purpose 'main machine'.

  • At a glance

    Windows 11 ProIntel® Core™ i5-520M8GB(integrated graphics) Intel HD Graphics
    Operating System
    Windows 11 Pro
    Computer type
    Laptop
    Manufacturer/Model
    Dell Latitude E4310
    CPU
    Intel® Core™ i5-520M
    Motherboard
    0T6M8G
    Memory
    8GB
    Graphics card(s)
    (integrated graphics) Intel HD Graphics
    Screen Resolution
    1366x768
    Hard Drives
    500GB Crucial MX500 SSD
    Browser
    Firefox, Edge
    Antivirus
    Defender
    Other Info
    unsupported machine: Legacy bios, MBR, TPM 1.2, upgraded from W10 to W11 using W10/W11 hybrid install media workaround.

    In-place upgrade to 22H2 using ISO and a workaround.
    Feature Update to 23H2 by manually installing the Enablement Package.
    In-place upgrade to 24H2 using hybrid 23H2/24H2 install media.
    Upgraded to 25H2 by Enablement Package.

    Also running Insider Dev, and Canary builds and Windows 10 as native boot .vhdx.
  • My SYSTEM THREE is a Dell Latitude 5410, i7-10610U, 32GB RAM, 512GB NVMe ssd, supported device running Windows 11 Pro.

    My SYSTEM FOUR is a 2-in-1 convertible Lenovo Yoga 11e 20DA, Celeron N2930, 8GB RAM, 256GB ssd. Unsupported device: currently running Win10 Pro, plus Win11 Pro RTM and Insider Dev, Beta, and RP 24H2 as native boot vhdx.

    My SYSTEM FIVE is a Dell Latitude 3190 2-in-1, Pentium Silver N5030, 8GB RAM, 1TB NVMe ssd, supported device running Windows 11 Pro, plus Insider Beta, Dev, and Canary builds (and a few others) as a native boot .vhdx.

    My SYSTEM SIX is a Dell Latitude 5550, Core Ultra 7 165H, 64GB RAM, 1TB NVMe SSD, supported device, Windows 11 Pro 24H2, Hyper-V host machine. Updated to 25H2 on 30th September 2025.

    My SYSTEM SEVEN is a Lenovo Thinkpad T580, Intel Core i7-8650U, 16GB RAM, 512GB NVMe SSD + 2nd 512GB NVMe SSD, a supported device for Windows 11. This is my current general purpose 'main machine'. The installed Windows 11 Home from my System One has been migrated to this machine.
infinity said:
Is Avast the absolute best compared to all others in detection rate?
Click to expand...
Avast, AVG, Kaspersky, Defender, are a few AVs that can detect fileless malware, some better than others.
 

My Computer My Computer

At a glance

Home26H2CanAMD Ryzen 5 8600G (07/24)2x32GB Kingston FURY DDR5 5600 MHz CL36 @5200...ASROCK Radeon RX 6600 Challenger D 8G @48FPS ...
OS
Home26H2Can
Computer type
PC/Desktop
CPU
AMD Ryzen 5 8600G (07/24)
Motherboard
ASROCK B650M-HDV/M.2 (07/24) BIOS 4.21 AGESA ComboAM5 1.3.0.1 (04/26)
Memory
2x32GB Kingston FURY DDR5 5600 MHz CL36 @5200 CL36 (07/24)
Graphics Card(s)
ASROCK Radeon RX 6600 Challenger D 8G @48FPS (08/24)
Sound Card
Creative Sound BlasterX AE-5 Plus (05/24)
Monitor(s) Displays
24" Philips 24M1N3200ZS/00 (05/24)
Screen Resolution
1920×1080@165Hz via DP1.4
Hard Drives
Kingston KC3000 NVMe 2TB (05/24)
ADATA XPG GAMMIX S11 Pro 512GB (07/19)
PSU
Seasonic Core GM 550 Gold (04/24)
Case
Fractal Design Define 7 Mini with 3x Noctua NF-P14s/12@555rpm (04/24)
Cooling
Noctua NH-U12S with Noctua NF-P12 (04/24)
Keyboard
HP Pavilion Wired Keyboard 300 (07/24) + Rabalux 76017 Parker (01/24)
Mouse
Logitech M330 Silent Plus (01/26)
Internet Speed
500/100 Mbps via RouterOS (05/21) & TCP Optimizer
Browser
Edge, Brave for YouTube, LibreWolf for FB
Antivirus
NextDNS blocking 1/3 Traffic
Other Info
Phone: Motorola Moto G86 (02/26)
Backup: Hasleo Backup Suite (PreOS)
Headphones: Sennheiser RS170 (09/10)
Chair: Huzaro Force 4.4 Grey Mesh (05/24)
Notifier: Xiaomi Mi Band 9 Milanese (10/24)
FlexCore USB-C 3.2 Gen 1 (M) to LAN (F) (08/25)
I would be more concerned why PC does not have Defender. Who knows what type of malware e.g. keyloggers have been installed already. Personally, I would not take the risk and teinstall from scratch and then change all online pssswords e.g. to bank, ebay etc.

Paranoia ? Maybe but can you afford to take the risk?
 

My Computer My Computer

At a glance

Windows 11 Pro + Win11 Canary VM.I9 13th gen i9-13900H 2.60 GHZ16 GB solderedIntegrated Intel Iris XE
OS
Windows 11 Pro + Win11 Canary VM.
Computer type
Laptop
Manufacturer/Model
ASUS Zenbook 14
CPU
I9 13th gen i9-13900H 2.60 GHZ
Motherboard
Yep, Laptop has one.
Memory
16 GB soldered
Graphics Card(s)
Integrated Intel Iris XE
Sound Card
Realtek built in
Monitor(s) Displays
laptop OLED screen
Screen Resolution
2880x1800 touchscreen
Hard Drives
1 TB NVME SSD (only weakness is only one slot)
PSU
Internal + 65W thunderbolt USB4 charger
Case
Yep, got one
Cooling
Stella Artois (UK pint cans - 568 ml) - extra cost.
Keyboard
Built in UK keybd
Mouse
Bluetooth , wireless dongled, wired
Internet Speed
900 mbs (ethernet), wifi 6 typical 350-450 mb/s both up and down
Browser
Edge
Antivirus
Defender
Other Info
TPM 2.0, 2xUSB4 thunderbolt, 1xUsb3 (usb a), 1xUsb-c, hdmi out, 3.5 mm audio out/in combo, ASUS backlit trackpad (inc. switchable number pad)

Macrium Reflect Home V8
Office 365 Family (6 users each 1TB onedrive space)
Hyper-V (a vm runs almost as fast as my older laptop)
cereberus said:
I would be more concerned why PC does not have Defender. Who knows what type of malware e.g. keyloggers have been installed already. Personally, I would not take the risk and teinstall from scratch and then change all online pssswords e.g. to bank, ebay etc.

Paranoia ? Maybe but can you afford to take the risk?
Click to expand...

Worth repeating. I agree. (y)


@infinity
 

My Computer My Computer

At a glance

Windows 10 Pro 64-bit 22H2 19045.4046Intel i7-3770 @ 3.40GHz8 GBAMD 7500 Radeon HD Series
OS
Windows 10 Pro 64-bit 22H2 19045.4046
Computer type
PC/Desktop
Manufacturer/Model
Dell/Vostro 470 (Year 2012)
CPU
Intel i7-3770 @ 3.40GHz
Memory
8 GB
Graphics Card(s)
AMD 7500 Radeon HD Series
Sound Card
Realtek Hi-Def Audio
Monitor(s) Displays
Dell U2412M
Hard Drives
1 TB 7200 HDD
Keyboard
Dell/USB
Mouse
Dell/USB
Internet Speed
100/10
Browser
Edge
Antivirus
Windows Security/MalwareBytes Premium
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