Probably a bios upgrade is in order.
Pentium D is like 2005.
I have a 3.0 Pentium D from Gateway.
The bios update from them helped.
Still an occasional blue screen crash when I install driver related software.
If you can run it in safe mode with networking,
use windows update and run it.
Update the graphics card from nvidia's site.
USA and Canada- http://www.nvidia.co...ge/support.html
Do you have a manufacturer that you can find downloads?
And since XP was having trouble as well I'd think to test the memory.
W7 has a built in memory checker, have you tried it?
After reboot with Windows 7 there should be choices off what to boot to.
If not, press f2 or whatever it shows for boot options.