Completely locks up, hard reboot required after 30-40 sec from startup

Hello,

I recently (about 4-5 months ago, so not very recently) upraded my system to Windows 7 64bit from Vista. Ever since then my computer has had issues where it locks up completely (unable to move the mouse, whatever sound was playing at the time loops) and a hard reboot is required in order to bring it back to order.

It usually wasn't a huge problem before, but for some reason it willl now proceed to lock-up within about 30-40 seconds of booting up the computer, after the desktop loads. I tried disconnecting my second hard-drive (I had bought a new one to install W7 on, and kept the old one plugged in) but that didn't make a difference.

It seems to boot fine in safemode, but I have no idea what the problem could be.

Any help would be greatly appreciated.

System specs:
Operating System: Windows 7 Home Premium 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_gdr.110622-1506)
Processor: AMD Phenom(tm) 9550 Quad-Core Processor (4 CPUs), ~2.2GHz
Memory: 4096MB RAM
Card name: ATI Radeon HD 5800 Series

I'm not sure what other specs you might need, but if I've missed something, please let me know! Thanks.

Thanks for the reply,

I tried both the disk check and what was recommended on the first link, but neither did the trick.

I would try the Repair Install, but it states in the instructions that you can not do it from safe mode, and safe mode is the only access to the computer that I currently have, as it locks up within 30 seconds from starting up.

Any ideas of what else I can try?