Fail to restart windows Guest after Linux power failure

[clfh]

I had a perfectly-working system comprising Windows 7 guest running on Linux (Mint).
We had a power failure in which the mains electricity spiked on and off for a few minutes.
On attempted reboot my BIOS had lost its record of which disk to boot from (and other data?)(there are 5 disks).

After I had selected the correct disk to boot from Linux booted OK.
But when then trying to re-start VirtualBox with Windows 7 Guest I got:

Failed to open a session for the virtual machine Windows 7.
VT-x features locked or unavailable in MSR. (VERR_VMX_MSR_LOCKED_OR_DISABLED).

I know that I can suppress this by disabling VT-x in VirtualBox, but I should not have to do this - it worked fine before!

(And if I do disable VT-x I get a "Windows is loading files" cycle).

My suspicion is that some other Boot Loader setting has been lost during this power failure - one that is required for VirtualBox to be able to use hardware virtualization.

Can anyone suggest what BIOS / Boot Loader settings I should be looking for to re-enable hardware virtualization? Maybe not the exact words, but likely terms.

My processor is 4-core Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz
I
TIA

[socratis]

I don't know what brand of BIOS you have. You'll have to look up the specifics in your BIOS manual. Look for VT-x, Hardware Virtualization or something similar. I did a quick search (you could too) and I found a small video that might (or might not) help.