Computer Crashes Every Time It Starts Up

First off, here are my computer specs (I like to get detailed): HP Pavilion a820n running Windows XP SP2
540J Pentium 4 HT, 3.20 GHz (1MB L2 cache, 800MHz front side bus)512 MB PC3200 DDR SRAM memory
200 GB 7200RPM Serial ATA hard drive.Intel Graphics Media Accelerator 900 with up to 128 MB shared video memory.Thats whats on the front of my tower. So, the title of this thread is self explanatory. I just turn on the computer and after it loads, after the desktop appears and right around when the desktop icons are loading, it just goes blank and restarts itself. Last night I did an error check for the hard drive, and it didnt come up with anything. I actually went to bed while it was scandisk or whatever, and when I got up, the computer was in its neverending cycle of resterting and crashing. I can, however, load it in safe modes, like with networking; that's what I'm using right now.