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Just had an instance where a Server 2008 R2 Hyper-V guest shut down unexpectedly, and was then on a blue screen of death reboot loop on restart. (The fact it was a guest VM is pretty irrelevant, the following instructions will work for a physical server, or indeed a client OS, as well).
The BSoD error was BAD_SYSTEM_config_INFO, with a STOP error of 0x00000074.
This generally means part of the registry is corrupted.
Hit F8 on the reboot cycle to get into the Windows boot options (and by all means try ‘Last Known Good Configuration’ before doing the following).
Select ‘Repair Your Computer’ from the top of the list, login with any local admin credentials you have, then select ‘Command Prompt’ from the available options.
Change drive letter to whatever it thinks your system drive is assigned to (may take a bit of trial and error, in this example it was D:)
Go into D:\Windows\System32\config and you should see a folder called RegBack (this contains backup copies of the registry hives).
Make a backup copy of the hive files in the config folder (e.g. DEFAULT, SOFTWARE etc) if required, then copy all the files from the RegBack folder to the D:\Windows\System32\config folder.
Exit from the Command Prompt window and then click Restart (and keep your fingers crossed!)
Even if successful I would suggest you consider the OS “at risk” from that point on – until you find out and fix what caused the problem in the first place – but hopefully this will get you out of the hole in the short term!
