hey people i have a small problem with my xp.. now this has always been a smallish problem with it but now its getting way worse. the system is just randomly shutting off... like if i leave it on for a night it usually will be restarted when i wake up. but just today when i was trying to start it up it gets to the desktop.. then about five or 6 minutes later it goes black, ive tried safe mode same result im scared to do a system restore because i would hate for it to go off in the middle of it. ive checked all the fans on it they are all working perfectly, and i have an older xp hard drive in it now and its working perfect too. anyone have any explanations for this? id love to get it working again

Dell Dimension 8200
intel pentium 4 2.8 mhz
256 DD..uhh actually i have no clue..its very weird ram
40g HD
Nividia Gforce 6200- i think thats how its spell :p
Windows XP home

Are you sure that the black screen is not just a "no screen saver" starting and by pressing any button you will get it back?
Try doing a disk check. Go, "Start" "My computer" right click "Drive *" (* = your drive with the faulty XP), "Properties", "Tools" tab, "Check now" put a check in both boxes, click "Start" reboot.
If you are still having trouble, go "Start" "Run" type in "msconfig" click "OK" click "Start up"tab" click "Disable all" Click "OK" click "Reboot" and check (Do not go on the internet as you have no security) If that fixes your problem, one of the programs is causing your problem, keep enabling some to run until you find the one and reinstall it.
If you are still having trouble, download Ccleaner, backup your registry and run.

yo, i know its not the screensaver, im mostly a self dependent person when it comes to my computers. but i am truly stumped in this. it is going fully off after 2 or 3 minutes, i have no time for it to start and download anything. thank you for replying but what you have said will not help me in any ways D: not trying to sound mean or anything but i cant do anything that youve said. ive established its a software error
i went and did F8->Disable automatic restart on system failure and found out the error it gets, im repeating this on memory so it might be off i believe it said "The windows subset has terminated unexpectedly at 0xsomething The system is now shut down" sadly i dont have an xp disk so its not as easy as just putting a disk in there, i dont have any money to spend on a new one and the warrenty is up on it. i will be throughly impressed if someone can come up with an answer to this. i look forward to your answers