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#31
You have problems that are most likely to be hardware. As such, swapping the mobo would be a good idea if you can do it without charge.
It could also be the Windows disk - is it an original Microsoft disk (with the hologram?). Where did you get the disk from?
Checking compatibility for all installed hardware and software may help: Windows 7 Compatibility: Software Programs & Hardware Devices: Find Updates, Drivers, & Downloads
Hardware removal (as suggested above) is the easiest way to figure out what's wrong - but you'll eventually reach a point where you can't remove any more hardware. If that's the case, then you'll have to guess what (among the remaining hardware) is at fault. Don't forget to try installing windows on the stripped down system to see if it succeeds there.