all of my files wiped?

I just turned my computer on, and it's as if I just bought it. All of the files I had have been wiped, the desktop background is set to default, the desktop is set out differently with different shortcuts.

My computer had been running really slow yesterday and kept crashing. I didn't change any settings or anything. Anyone know what might have caused this and if there is anything I can do to get my files back?

and now they seem to be back once i restarted? weird? except the desktop background is different. computer seems to be running much faster than it was yesterday...

You may have accidentally logged into the local profile if your PC is on a domain, or the guest account?
The desktop background changing randomly could indicate a problem with the %appdata% folder perhaps

Yeah, maybe you somehow ended up logged in as the "guest" user rather than your self.

XP is really good at corrupting your profile and logging you in under a 'temporary' account. it will throw up a message saying that if that is the case - if it is, backup all your shit, reformat.