Odd crashing

Well, I just recently added a new HD to my system that I ripped from an old Dell, both it and my old HD are sata. Being a student, once I saw and validated the 30$ windows 7 offer from Digital River I took downloaded the installer and installed to the older dell HD.

After the install, I messed around for about 20 minutes and everything was fine. However after the 3rd install the OS began crashing after about 2-3 minutes. After the 4th or 5th boot it started crashing about 5-10 minutes in. Now on my 10th or so boot it crashes after about 20 minutes. The crash is almost sure to happen as I have only been able to shutdown once before a crash.

I am dual-booting XP and 7, XP being the default for the time being.

I've been looking on the inter-webs for solutions, and I have contacted mircosoft for support to no avail.

I can give any other information that would seem useful.

Any help would be much appriciated!

Thanks, Steven

Edit: The crash is more of a freeze, the HD activity light stops and the screen freezes. This has happend while both browsing, sitting inactive, and right after logging in. (Task does not appear to affect crash)