blue about blue screen

[trunk]

Here is my problem, sorry for the length, trying to give details:

My computer recently wouldn't boot up out of the blue, it would go the "windows not shut down properly window" with the options to boot normally, last know config, safe mode, ect... Regardless of which option chose it would slowly try to boot then flash a blue error screen to fast to read and reboot to do the same again. In safe mode, the last thing the screen showed loaded was agp440.sys then the reboot. I haven't installed any new hardware recently, the last was a PNY geforce 4200 AGP card (and drivers) over a month ago, and the computer ran perfectly till this week. When I originally installed the card before Christmas, I had a problem (may have been similar, I don't remember now) after a couple days of computer use so I reinstalled XP then (with SP1 and all my software & games). My computer did work perfectly for about a month untill this week (though occasionally with a hiccup where it would "pause" for a second). Thinking it was a software problem, I reinstalled XP completely and rebooted. It started normally, I then installed the geforce drivers and rebooted, no problem, I could use XP. I then proceeded to install SP1, in the midst of installation it rebooted and upon reboot I get the same problem, except the blue screen stays this time saying an "unmountable boot volume" and no reboot. I'm trying to narrow down the problem but getting exhausted reinstalling Win XP. Using another drive with XP, I can't view the contents of this main drive or even with the command prompt in the recovery console. It shows C: but won't list anything. In the bios, the only thing I found is that both a network card and the video card have the same IRQ (?), you can change it from 3-4-9-11 but the two are linked and can't be changed seperately. I can list all my bios settings, but I've played around them and nothing solved the problem. To me the problem points to the video card which, however, did work fine for a while (under alot of heavy gaming too) or the hardrive since the unmountable boot volume message I keep getting, but I can install XP and use it on it (for a bit anyway). In the Xp install I always reformat C: with NTFS (long version) through the cd, not with fdisk.

My question is, does the above scenario point to a problem with the video card, SP1, or the hard drive? Just looking for some direction. Thanks!!!

Here is the comp specs:
Dell P4 1.3, 512 DDR, 2 drives, Device 0 is 60 gig, Device 1 is 80 gigs. PNY Gefore 4200 128 DDR