Computer Problems. Keyboard locks up, screen scrambles. Can't reformat.?

[Jayman77]

I'm having an issue w/ my gaming computer.
-Problems:
-When It starts up, I cannot reformat because my keyboard locks up and turns off so I can't boot from CD.
-Occassionally the windows xp screen will pop up and then immediately afterwards the screen is scrambled w/ vertical patterns and I can't see anything on the screen besides the scrambled mess.
-The computer will not get past that point. It will not start and I cannot use the mouse or keyboard.
-After a few minutes of the screen being scrambled my monitor switches to analog and then the screen turns black while the computer remains on.
- I tried a different monitor and no luck... i'm sure its not the problem b/c the windows xp screen is fine.
-Not the power supply because it starts up and doesn't shut down.

Any ideas on whats going on w/ my computer? mb its time to buy a new one. Thanks for your help.