Need Advice on dual Boot Win 11 Pro and Win 10 Pro Computer

I have retrieved some info from the Dell XPS 8930 computer; hope this both sufficient and helpful.

UEFI with Legacy OPROM Secure boot Off

BIOS: 1.1.31

SATA Operation: RAID "ON"

Firmware TPM disabled (option greyed out).

IIRC, when I tried to switch from RAID to AHCI, the computer refused to boot and I had to get some help.

This is why I believe it necessary to re-install Win 10 Pro after first setting BIOS to AHCI, and then enabling features which will allow TPM to work or be installed/updated. After Win 10 Pro Installed, then I'll Install Win 11 Pro and set-up as Dual boot. Sound good?

In that case, yes, switch to AHCI, reinstall Windows 10 and then 11. I would first upgrade the UEFI firmware (aka BIOS) and install the new 2023 certificates, but not revoke the old 2011 certificates yet, so you can boot both old and new UEFI mode disks. Install Windows 10 64-bit, make sure you install all drivers and new 2023 certificates. Install Windows 11 and new 2023 certificates. Enable Secure Boot. Verify that both Windows versions have new 2023 certificates and that they boot fine without warnings. Revoke the old 2011 certificates. Check dual boot is still working fine with Secure Boot enabled. If you have any old USB flash drive or bootable external USB disk that cannot boot because of old 2011 certificates, temporarily disable Secure Boot.

RIBob said:

I have retrieved some info from the Dell XPS 8930 computer; hope this both sufficient and helpful.

Click to expand...

I wouldn't reinstall Windows yet, and I wouldn't change SATA Operation from RAID On to AHCI at this point. AHCI is not a Windows 11 requirement.

The fact that Firmware TPM is greyed out may be related to Legacy Option ROM being enabled. On the XPS 8930, disabling Legacy Option ROM can make Firmware TPM available.

Before changing anything, though, we need to determine how the existing Windows 10 installation is actually booting.

Please run msinfo32 in Windows and tell us what it says next to BIOS Mode.



Also, please post the requested screenshot of Disk Management and the WhyNotWin11 results.

If the Windows disk is MBR and Windows is booting in Legacy mode, that needs to be dealt with before disabling Legacy Option ROM. If it is already GPT and booting in UEFI mode, reinstalling Windows may not be necessary at all.

I believe that problem with existing version of Win10 Pro OS is related to it (along with multiple associated progs) being configured with RAID system as opposed to AHCI. It was when trying to switch from RAID to AHCE that I encountered massive problems, requiring Professional intervention in order to get the damn thing to boot.

RIBob said:

I believe that problem with existing version of Win10 Pro OS is related to it (along with multiple associated progs) being configured with RAID system as opposed to AHCI. It was when trying to switch from RAID to AHCE that I encountered massive problems, requiring Professional intervention in order to get the damn thing to boot.

Click to expand...

That explains why Windows stopped booting when you changed RAID to AHCI, but I don't think you need to change that setting.

Windows was installed while the SATA controller was set to RAID On, so changing it to AHCI afterward can prevent Windows from booting. However, AHCI is not a Windows 11 requirement, and RAID On does not prevent TPM 2.0 from working.

I would leave SATA Operation set to RAID On for now and concentrate on determining the current Windows boot mode and disk partitioning.

Please post the msinfo32 BIOS Mode, the Disk Management screenshot, and the WhyNotWin11 results.

I think, at this point, my goal is re-configuring computer BIOS (allowing ACHI instead of existing RAID) in order to install a brand-new Win 10 Pro OS, and then a Win 11 Pro OS. My intent is to have both OS available on demand. Tell me how I'm wrong, here, please.

Before recommending how to proceed, we need to know exactly which Windows 11 requirements the computer currently fails.

Please run WhyNotWin11:


The results are shown in green (compatible), red (unsupported), or yellow (warning/possible issue).

Tell us which items appear in red or yellow, for example:

- Boot Method (red)
- Disk Partition Type (red)
- Secure Boot (yellow)
- TPM Version (red)

There is no need to list the items shown in green.

Even if you cannot make the computer Windows 11 compliant, you can always bypass compatibility check and force install Windows 11. My main PC (2nd system specs) is an unsupported 3rd generation Intel Core-i7 3770, Legacy BIOS boot (on purpose, it also supports UEFI boot), no TPM, no Secure Boot.