AMD chips

[Anton]

Hey all,
Can anyone advise me on a little issue I have... My machine is running 
an athlon xp2000 chip (though something suspiciously similar happens 
with the wife's duron 700 also). Whenever I start to do some serious 
processing the machine just freezes. It happens in XP (more in 2000 
though) and heaps in Linux. Particularly it goes almost immediately when 
transcoding dvds (both xp and linux) and only lasts about 15mins when 
watching any kind of movie on linux (can usually get through a movie on 
xp). Now I happen to have a variable speed fan. The above only EVER 
happens (absolute 1:1 correlation) when the fan is on low speed - 
anything above about +50% speed on the fan and she just purrs away like 
a cat. The problem being the fan is damn noisy! I have gone into the 
bios and investigated the chip temperature cutout setup and have tried 
various things, but have been loath to turn off the anti-fry protection 
altogether... I don't want it to fry after all. You are of course 
thinking, he (or a mate...) has set up overclocking and this is normal - 
not so! A friend made sure that I had a variable fan should I want to 
overclock, but we never actually did it. It is running at its 1.6gig and 
still overheating, at least I can't imagine what else it could be. So 
any ideas? There are a couple of different temperature measures but I 
can't seem to figure out what they are really doing, as one looks like 
it should be cutting out at 72deg, but is fine at 75, and when set to 75 
also seems to cut out at 72. I do, of course, have to reboot, but i 
expect the temp usually doesn't drop too much in the 25 secs it takes to 
reboot into the bios. There is another temperature gauge in the bios 
which has (ASCII) after it, and this is set a little higher. What is a 
maximum that a chip should ever get to (on any gauge)? It would be good 
not to have to have the fan making such a din all the time, as there is 
no point just turning it on when needed, cos I never seem to remember, etc.
Any help much appreciated.
Cheers
Anton
ps has a soltek motherboard...