XP Freezing/not loading; HELP

[General Failure]

Right, so a couple of days ago my computer has begun to act strangely out of the blue.

When I turn it on, all I will get is a black screen and nothing will happen, despite the computer sounding like it is booting up/fans running/etc.

IF by some miracle I make it past this point, the computer will randomly freeze on me. Sometimes it works long enough for me to use my web browser/check emails/whatever. However, other times it will freeze before making it past setup. If it freezes, nothing will work at all (IE If I hit capslock/numlock, it will not light up on the keyboard)

I really doubt heat is an issue here, as I have the side panal off and have a fan blowing on the motherboard/video card/etc.

SPECS

Windows XP media center edition
AMD Athlon 3.4 ghz processor
GeFOrce 8800 GT gfx card
Dynex 400W power supply
1024 RAM
Unsure of the motherboard; sorry
Avast Anti-virus

HELP ASAP would be greatly appreciated, as I need this computer for school.

One final irony; The first time I went to post this on a different computer it randomly restarted on me. Ffffffffffffff--

*EDIT*
Forgot to mention antivirus

[Kevin_gibson]

How long has this been going on for? Have you installed anything recently? Or changed anything? Can you get into safe mode? If can does it work ok in here?

[wgnick]

see if Avast has an XP boot disk or download that you could burn on your different computer. Run it and see if you get into the safe mode command prompt and run chkdsk