General Computer Suckfest

Basically my room mates younger sister has completely screwed up her computer. Don't know what she did, but for some reason I can't install, open simple things like "regedit" or even move/rename files. It's a Sony desktop with Vista OS. No she doesn't have any anti-virus so I can't even scan for viruses >_>

Can't run system restore either. I am seriously baffled at how messed up this seems to be right now...

Okay to clear up what you said please check these

Does the Computer start

Does the Computer boot normally

Can the Computer Access the Internet

Can you do a System Restore

If you cannot install programs, i suggest you try using portable programs that do not require installation
(like...go to your computer and download a portable version of some virus detection and removal programs, "Install" them and put them onto a flash drive)
[SIZE="1"]By install i mean unzip, they just call it install[/SIZE]

I have not used these programs but i trust the website and their programs they list
http://portableapps.com/apps/utilities/s...r_portable "advanced spyware detection and removal tool"
http://portableapps.com/apps/utilities/clamwin_portable "antivirus to go"