I recently performed a BIOS upgrade on my Dell Latitude E5540 laptop. This had a couple of unanticipated consequences.

Firstly, Microsoft Bitlocker wouldn’t run – it recognised a hardware change and required the recovery key to be entered before it would proceed. Thankfully I had saved this into OneNote and could access this from my phone.

Secondly, my VM’s would boot in Hyper V. I was getting a message along the lines of : Hyper v failed to restore VM XXX using processor-specific features. The virtual machine ‘<VM Name>’ is using processor-specific features not supported on physical computer ‘<Hyper-V Host>’.

This one stumped me for a while. I googled various options and tried some solutions, including helpful (but unhelpful) ones suggesting that during the BIOS upgrade some BIOS options had been changed and I need to go and change them back. I spent an hour going through all of the options, but for the life of me could not identify any that had changed, and if they had I certainly had no idea.

In desperation I decided to create a new VM, and point it back to the existing virtual disks. This probably would have worked, but in the process of doing this I noticed that in Hyper-V manager if I right clicked on my existing VM there was an option to reset the state. This worked like a charm and the problem was solved, now the VM booted from scratch. Simple really when you know how.