Windows 7 Freezing on startup

Ok, I am having a freezing issue with Windows 7 that I need help with. I'm not sure if it is a software problem or a failing HDD!

My computer has worked flawlessly (for the most part) for about 4 years now, but it suddenly froze one day on the Windows 7 startup "splash screen", and won't boot past that! I can get it to go into the repair portion with the disc, but then it either freezes again, or says something like "Windows Can't Repair the Disc". I thought maybe the hard drive was failing, so I bought a new one, and used the old one as a slave to try to pull my files off the old one! The old one shows up on my desktop, but as soon as I try to open any files, it freezes again! I don't know what else to do, and I'm not that good at computer issues, so if anyone has any suggestions, they would be greatly appreciated! Thanks!

Here is what I have:
Abit KN9 SLI motherboard
AMD Athlon 64 X2 4400+ 2.3GHz processor
320 GB Seagate HDD
6GB memory
Windows 7