To clarify, if there was a Windows 11 compatibility check, it would display an error at first screen and stop before even showing the disks to choose where to install. Besides if the USB was created with Rufus, it would skip compatibility check. If it was an attempt to install 25H2 on a CPU without SSE4.2, the USB would hang at the blue Windows logo without the spinning curves, but the OP managed to start installation which failed at 70%. This indicates it is some other compatibility reason, neither SSE4.2, nor the initial compatibility check. Apart from the known issue for the installation to fail if there are two or more disks connected, there is also the possibility that Windows Update tried to install a driver or some other update which failed leading to the whole installation to fail. Even if you click on the initial message "Change how updates are handled" (or similar) and select not to install Windows updates during the installation, I don't trust it. It is better to stay disconnected from the internet (remove the LAN cable, disconnect from Wi-Fi or switch if off) until the installation is completed successfully. Even if Windows doesn't attempt to install any updates, there might be a hidden online compatibility check somewhere during the process and force the installation to fail. Staying disconnected from the internet avoids this risk. Also Windows might try to install drivers for some device and fail. To make sure this won't happen you can disable some devices in BIOS (sound, LAN, Wi-Fi, camera, card reader, second disk). For everyone upgrading from Windows 10 or older Windows 11 version you can disable these devices either in BIOS or Device Manager before starting the upgrade. Again make sure you stay offline and also disable all startup applications, all customization applications and any third-party antivirus, antimalware and firewall.
TIP: For those with a small SSD, such as 120GB, where every MB of space counts, you can install Windows 11 on MBR which uses only a single system partition compared to GPT. You can also manually prepare the disk before installation so you create a single NTFS partition on the whole area of the disk without giving Windows the chance to create the small system partition and consume valuable space. I can assure you Windows 11 works fine without it and you will notice no incompatibilities or other issues because this partition is missing since Windows writes the respective data on the Windows partition. If you want to do that, at first Setup screen, before you start installation, press
SHIFT+
F10 to open a Command Prompt. Click inside so you can type and execute this code:
Code:
diskpart
list disk
select disk 0
clean
convert mbr
create partition primary
list partition
select partition 1
format fs=ntfs quick
exit
exit
The first line loads Disk Partition utility. Then it shows the available disks, assuming there is only one, the Windows disk should be disk 0. Check by size. The next command deletes all partitions, then it converts to MBR (if not already). Then it creates a single partition and displays the list of available partitions. We select the first partition (there should not be any others) and quick format it to NTFS. Then we exit Disk Partition utility and then we close the Command Prompt window. At this stage you can proceed with the installation. I couldn't see any disk choosing screen on the modern 25H2 Setup, so I always click to switch to classic Setup, just in case. I recommend to switch to classic Setup too. After proceeding and skipping compatibility check you should see the disk selection screen. The Windows disk should have a single NTFS partition. Choose that and proceed. Don't reformat the disk or delete the partition, or Setup will create the small system partition. After successful installation you can search for Disk Management and load it to confirm the Windows disk has a single NTFS partition. You will have absolutely no issues doing that, I have done it many times
