The user profile directory? Almost everything is in there somewhere.
Not that it matters much. If the PSU went out and took everything with it i'd only lose a few hours work.
It'd be annoying but i'd probably be a lot more annoyed with having to replace the hardware.
It'd only take a few hours to restore from backup but it'd take several days to get a similar machine.
Realistically if this thing goes out i'm just going to spin it up in a VM on one of the other machines I have on hand until I can find a suitable upgrade to replace it with rather than trying to put it back like it was as it's long overdue to be replaced anyway.