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Hi all, I am tearing my hair out on this one. Windows 10 host (64-bit, build 21H1) running on a Thinkpad T480s, clean Windows install with only Lenovo System Update installed and all drivers/fw/BIOS up to date. Followed all the steps in the FAQ guides but my Win 7 64-bit VM is suffering from incredibly poor performance, turtle icon and the logs show it is falling back to NEM (Attempting fall back to NEM: VT-x is not available).

To confirm:
Intel i5-8350U supports VT-x
Intel virtualisation and VT-d both enabled in BIOS
64-bit VM OS
OptionalFeatures.exe shows that none of the listed components are enabled
Also ran in elevated cmd: bcdedit /set hypervisorlaunchtype off
Also ran: DISM /Online /Disable-Feature:Microsoft-Hyper-V
Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-Hypervisor <-- I did try the -All flag but that failed, this line ran though
Set the group policy "Turn on Virtualization Based Security" to Disabled
Checked that Core Isolation Details are set to off
Rebooted several times having made the changes
Bcdedit shows the launch type as off but systeminfo shows "A hypervisor has been detected"

The only thing I have not been able to do is temporarily disable secure boot as my BIOS is protected. Log attached in case it helps. TIA

The bcdedit command only sets the flag to not load the hypervisor when the PC boots. You need to do a complete powerdown/reboot to get the OS loaded without the hypervisor. You may need to do it more than once. Until you achieve that you will still get the falling back to NEM message because the hypervisor is still active.

If all else fails, remove the battery from the PC while it is shut down, then boot it.

BillG wrote:The bcdedit command only sets the flag to not load the hypervisor when the PC boots. You need to do a complete powerdown/reboot to get the OS loaded without the hypervisor. You may need to do it more than once. Until you achieve that you will still get the falling back to NEM message because the hypervisor is still active.

If all else fails, remove the battery from the PC while it is shut down, then boot it.

Thanks, I did already try that by powering off, removing the charger and using the power reset hole which disconnects the internal battery but I will open it up and physically dc the battery. Fast startup is off too.

Did you try Control Panel --> Programs --> Turn Windows features on or off. In the Windows Features dialogue box, scroll down to "Hyper V" and ensure it is unchecked.

I opened the laptop, removed the battery, pressed the power reset button and held the power button for 30 secs and left battery dc for an hour. Put back together but same issue when running systeminfo in cmd.

I ran the turn features on/off and everything Hyper-V related is already unticked as this is the same box as optionalfeatures.exe.

The only step from any guide I have found that I have not been able to test is to temp disable secure boot but that was a footnote from the Petri site and not listed on here in the FAQs. I will try putting the SSD into another laptop that I do have access to the BIOS and see if it helps.

One thing to try is to go back to 6.1.30 and give it a go, but it may not work.

VB 6.1.32 has issues with hyper-v and on my setup if I use VB 6.1.32 and have hyper-V enabled the guest runs very slow. I had to revert to 6.1.30 as it worked with hyper-v on my PC. I need hyper-v as I use WSL2 for development purposes.

Make sure you use the same guest additions for the version of VB you end up with.

AndyCot wrote:One thing to try is to go back to 6.1.30 and give it a go, but it may not work.

VB 6.1.32 has issues with hyper-v and on my setup if I use VB 6.1.32 and have hyper-V enabled the guest runs very slow. I had to revert to 6.1.30 as it worked with hyper-v on my PC. I need hyper-v as I use WSL2 for development purposes.

Make sure you use the same guest additions for the version of VB you end up with.

I had tried going back to 6.0.6 as this worked with the same VM but then I had errors when starting the VM. I just pulled the SSD and put it into the same model of laptop but where I have access to the BIOS, I booted (without making any secure boot changes) and it worked straight away so there is obviously something in the BIOS that is the issue, possibly the secure boot off then on would fix. Will compare the two BIOS settings and see if anything obvious is different. Thanks

I have ended up clean installing Windows 10 onto a T480 that I have here and without making any changes to Windows settings/features, Hyper-V is showing as disabled in systeminfo and in VirtualBox the VM runs smoothly with no turtle icon. It must have been a BIOS issue on the original laptop, thanks for the messages.

Ah, the good ol' clean install. Glad you're up and running!

Simple07 wrote:Did you try Control Panel --> Programs --> Turn Windows features on or off....

This rarely kills off all the services calling for Hyper-V. See HMR3Init: Attempting fall back to NEM (Hyper-V is active)