I'm trying to fix a Windows installation that won't boot, but I think part of the problem fixing it is that it was hibernated, and thus is still sort of locked to access.
Is there a way to unlock it? Any caveats to it?
You can use a Linux live disk that allows hard drive access and delete the file called
The main downside is that this is the equivalent to forcefully shutting down the machine, anything open will be unsaved, and possibility of breaking things that were in the process of being updated.
As for unlocking it, I really need to know more - how far you get and what the specific errors are.
Some suggestions here.
Most of the time this is file system corruption that can be fixed by doing a:
from the recovery environment command prompt.
If chkdsk fails to get it booting do a "FixBoot" as described in this article.
If it is a OEM PC, Dell, HP ect, do not use the FixMBR command.