Major crash, pc now thinks it is new..

Hey, My pc recently had a major crash, it locked up, and gave me a bsod (I was on paint, so i dont know how it crashed..), instructing me to reset my pc. I did so, and when i get to the login screen, it takes 3mins to login, thats one of the first things i notice. The next thing is, everything from my desktop is gone appart from programs.
The pc litterally thinks that it has just been installed, it shows me the guide to xp, all the default stuff is up etc, just like you would see when you do a fresh install of xp. The annoying thing is, my files arent gone, they are still there, but my computer has made a new mydocuments folder, and is using this one as a new folder.. it wont let me change back to the old one (i dont know how). And to make it worse, when i turn off my pc for the night, and come back to it, it repeats this whole thing, it deletes all the files from the new mydocuments folder it made, so i cant keep anything on the desktop, or in my bookmarks etc.
I know it has messed up my registry, as i tried playing a game, but it insisted that i had no cd-key.. this happened on all my games
I tried a system restore to see if it would go back to normal, but it failed and this problem has still continued..

Pc specs:
Windows xp sp2,
Amd athlon xp 3200 (2.19GHz)
1gig of ram
ati 9800 pro

Can you help me?
Will i have to backup all of my files that werent deleted and just do a fresh install of xp?
please reply.
(if this is in the wrong section, please move it to the correct area )
If it is just a simple fix with the xp disk repair function, then i will try (still trying to find the thing )

 

You can try this, not sure if will work, but the easiest way to fix the registery without doing a repair. Go to Start, Run, and type in sfc /scannow. Make sure your windows xp disk is in your CD Rom drive, and hopefully that will fix the errors in your registry. Make sure there's a space between sfc and /scannow. If that doesn't work, you'll have to do a repair on it. To do that follow these steps:
Best to do a repair install ...."enter" when you are asked if you want to boot from cd (having put the cd in the drive ahead of start up) ...after files load, choose new install not "R" (that R takes you to recovery/ not repair) ...f8 to agreement ...then when it finds the previous install it will prompt for new install or repair "R" ...now hit "R" ...will save all your files and progams ...but loose all your updates. Hope that helps you.