Computer Problem Please Help

Here's the problem. I built this computer about a year and a half ago. It worked fine at first. Then I flashed a new bios and it started rebooting in the middle of my games. I have been trying to fix it myself for about a year. Whenever I try to play a game it reboots in the middle of the game. I thought it was the ram so I got Corsair to replace it. It still freezes in the middle of a game. It still plays the music but the game freezes. I have all the newest drivers and the newest bios. I will send the person who solves this problem for me $20 dollars. I am willing to try almost anything, apart from buying a new computer. My specs are:

AMD Athlon 2100+
Gigabyte GA-7VRXP
Corsair 512MB PC2700
Creative Labs Sound Blaster Audigy
ATI Radeon 9500 Pro
Pioneer 16X DVD Drive
Plextor 40/12/40 cd burner
Windows XP Pro

this is just a shot in the dark but try taking out your audigy card and using the onboard sound.. ive heard of people having probs with soundblaster and via combos...
thats the easiest fix (if it works) otherwise you want to look at your bios setting make sure you arent inadvertantly overclocking something.. maybe running the ram at timings it cant handle? what are your temps and what is your watts (psu)?

i would try going back to the old bios and reformating your hd both at the same time, don't install the sound card (just in case) or any other unnessesary drivers, instal a game and try running it,
but while instaling new os go into bios and check ram setting, go for auto or set them very lax, also check the speed of your processor, or even underclock it.

sorry I can't think of any specific problem but the above could work, if not.. then it's hardware,

by system temp do you mean mb? because that sounds high to me
p.s. if the above doesn't work, try borrowing a graphics card from a friend and try using that (or do this first, it's a little less work)

It only freezes after playing games. I can do anything else on it and it won't freeze. I don't see how the processor could overheat that much after just a few seconds of playing.