Okay, I found a ridiculously complex procedure for doing a manual System Restore.

But.. barf..

So I've booted from an Ubuntu LiveCD, mounted the NTFS partition R/w, and done what I think is the equivalent, but much simpler:
Code:
1. Backed-up files from /WINDOWS/system32/ to /old_config/

2. Did manual registry restore to the most recent restore point:

cd /System Volume Information/_restore{0F35CCEB-9975-48E3-8E59-CC599DCDBAC7}/RP102/snapshot
cp _REGISTRY_MACHINE_SAM /WINDOWS/system32/config/SAM
cp _REGISTRY_MACHINE_SECURITY  /WINDOWS/system32/config/SECURITY
cp _REGISTRY_MACHINE_SOFTWARE /WINDOWS/system32/config/software
cp _REGISTRY_MACHINE_SYSTEM /WINDOWS/system32/config/system
cp _REGISTRY_USER_.DEFAULT /WINDOWS/system32/config/default

Does that look about right?

Going to reboot and try it shortly here..