Not very clear what the issue is here.
When startup repair said it was unable to repair - did you scroll down to see the reason ?
It might say there is a possible corrupted registry.
If so - you should be able to replace it by copying the hives from the backup in windows\system32\config\regback
to
windows\system32\config - just overwrite the existing hives in the config folder.
The hives are called Default, Sam,Security,Software,System
Have a look and make sure the backup hives are not 0kb first.
You might find it easier to use notepad:
at cmd type notepad
when notepad pops up, select FILE>SAVE then choose ALL FILES instead of .txt files in notepad dropdown box.
You can navigate about with that.
Open 2 instances of notepad to make copying easier.
nb - if that doesn't work for you , what o/s are you using right now to post up here?