Please Help! Computer Freeze problem

[ssynesthesia]

Hi, I have a problem but i dont know what its related to so im trying this forum. I use a 3d application named XSI. I have a problem with XSI 4.2, right in the middle of my work (moving vertices) the whole computer freezes. No blue screen of death. Nothing. Frozen. I get no error messages. Somtimes I get a grey screen and somtimes it just looks like the previous screen except with squigglies. I have reinstalled Windows XP Pro Inbetween problems. (Although the Big Problem is new) The BIG Problem: The computer doesnt start back up it just sits there and doesnt load (just the blinking underscore) unless I go into bios setup and wait for a little while. I then leave it and Windows starts back up as if nothing happend. My specs: I have an AMD Athlon XP 3200+ with 768 mb ram, an ATI Radeon 9200 w/ 512mb ram, and Service Pack 2. On a Compaq. I thought this could be a video issue but I've reinstalled the latest drivers. My computer temperature is at 40c to 45c respectively. What can I do to fix this???