Well, I THINK I know what is going on here. I may be wrong.... There might be some driver issue here (VIA 4-in-1's) that are causing this instead. But, here is my guess.
Simply put, Win98 can't do a "halt" on the CPU. If a process is "running" in Win98, it runs the CPU wide open. It doesn't hog it all just to do nothing, it will multitask (sorta.. Win98 sucks at it) but the CPU basically will run wide open wether needed or not. If that process is waiting, the CPU still goes full out, just doing nothing instructions, but still processing and generating heat. Win2k can execute a halt instruction whenever the CPU is not busy and basically stop it from generating heat. (We are talking very tiny time slices here.) So whenever the CPU is waiting on the disk system for example, in Win2k it gets shut off, where as in Win98 it's still going nuts cranking out heat. This is why programs like RAIN and CPUIdle help keep Win9x systems cooler, because they detect when Win9x isn't really doing anything and shut down the CPU.
That said... if the CPU really IS under 100% load, Win2k should heat it up just as badly. That means if you are playing a game like AH that is really pushing your CPU, the Win2k box will heat up badly as well. Either way, you have a heat problem. Time to look at your heatsink/fan and how it is attached.
