While Windows NT based operating systems use the HLT instruction while the CPU is idle, Windows 95 and 98 (and maybe Windows ME) do a busy loop instead, which tends to use more power and run hotter. There are a few programs available that are able to run HLT instructions to sleep the CPU when it is idle, and supposedly make Windows 9x run cooler.
http://www.benchtest.com/cooler.html
I'm wondering if anyone has experience with these programs on actual hardware, and knows if they are worth it to save power and reduce CPU temps.