Sudden Vista Premium problem after 1+year

I have a Compaq Presario PC SR5130NX with original parts except upgraded RAM to 1.5 Gigs. I have had no problems for a year and three months roughly and all of the sudden it started locking up with almost any program I would try and run (Word 07, IE, Excel 07, games, etc.). At first I thought it was a virus so I ran McAfee several times after locking down my firewall and came up with nothing. I heard that Norton could cause a problem after the trial periods came do so I completely wiped the drive clean of all Symantec and Norton traces. I noticed a significant improval for about a week and then it went back to freezing with every program and started freezing when coming out of sleep mode. I tried doing the restore point to a month before, no luck, then I tried to reformat the computer (has separate partition on HD for Windows Recover) and it kept failing at 45% then on the fourth attempt it finished after about 12 hours. I ran the system diagnostics thinking it could be the HD or the RAM but the check came back ok(as well as the processor). I just recovered the computer again and I have nothing but a half installed WOW client, having all the problems from the first time before I tried to recover. Any suggestions out there?
~ BTW I have two other PCs, one with Vista Home Basic, and Laptop with XP if I need to test on either one of those.

If you've reinstalled from the recovery disks, then all should be well. This leaves a problem with the recovery disks, or a hardware issue.
I'd suggest getting another set of recovery disks from Compaq and trying them. If you still have problems, then it's most likely a hardware issue.