Sharing the scenario where after the power outage one of our Windows 2008 R2 server was not booting up. Mother Board of the server was replaced by the vendor as it has gone bad but after that server was sticking on the Recovery Screen.
We have tried few things but what eventually resolved the issue is below:
1. Boot with windows 2008 R2 media.
2. Go to System recovery option & select command prompt.
3. If command prompt doesn't arrive than you can just use shift + F10
4. Enter sfc /SCANNOW /OFFBOOTDIR=c:\ /OFFWINDIR=c:\windows
OFFBOOTDIR=c:\ --> Boot volume is c drive in our case
/OFFWINDIR=c:\windows --> windows is installed in c drive
This command is doing a offline scan of missing/corrupted files using sfc.
If repair is successful, You might need to add product key when system boot up normally as it will state that some unauthorized change has been made to the system.