Hard Error message on a GX270

Hi,

 

I have had my GX270 for about 4 years. No modifications. The power supply was replaced under warranty with original Dell part about 1 plus year ago. Processor 3 Ghz, memory 1 GB, and a 128 ATI AGP in the AGP slot installed by me when brand new. Never had any problems. This pass weekend I turned on the PC (usually on stand by, but sometimes is off for a week or so) it did boot up to XP and shorlty after I got  a blue screen with a Hard Error message. I hold down power and reboot again fine after that. I did not write down the number it displayed. I am wondering what it might be? memory, do i need to reseat? HDD maybe? Any ideas appreciated.

 

Chris