Not saying this will help your issue, butt it would not hurt to check.
Open the case, look at the back of the cd rom, unplug the power wire from the cd rom. (power wire = red,black,yellow ext..) (if you have 2 cd roms unplug both)
A pic of the power wire and cd rom
this may help us eliminate a power supply issue. there is a really large variety of problems that can cause this sort of behavior.
Boot computer, it may ask you to press F1 to continue.
This will make sure the ram is good.
To start the DirectX Diagnostic Tool:
1. Click Start, and then click Run.
2. In the Open box, type dxdiag, and then click OK.
under each tab, run the tests, if there is a problem it will show up at the bottom in the window.
Could be Heat, open the side of the case and use a house fan blowing inside the case to see if that helps. if so add more fans
is the computer dirty inside? visit radio shack and buy a can of PCB cleaner (printed circuit board cleaner)
1. unplug the computer from the wall
2.let stand for 30 minutes
4. spray everything starting from the top to the bottom (making sure you get that cpu fan and heat sink really clean) (don't worry its safe)
5. let it dry for 30 minutes (almost evaporates immediantly).
SiSoftware Sandra Lite 2007.SP1 (10.105)
It is a benchmarking, testing, and listing modules. run it use it to test. (it has several testing programs such as hard drive,memory ext..)
Well that should keep you busy