I am completely confused on this one. Pentium 4 2.4c HT w/ stock retail cooling I had previously been using Windows XP with this computer and had too much garbage installed so I decided to reformat and reload. I also decided to go back to Windows 2000 just because I seem to like it more. The whole time I was using Windows XP for a couple of years now atleast, my CPU idle temps were around 37 degrees celcius. I was pretty happy with this for stock cooling. I have always been using MBM to check my CPU temps. Now that I have installed Windows 2000 my idle temps have been around 52 degrees celcius. That is quite the jump. I know this is still in the allowed limits for this processor but I am completely confused on why this is like this. I checked to make sure there was not some process running in the task manager. The cpu % stays at 0 and the temperature will not drop below 50 at all. There was absolutly nothing changed with the hardware with the reformat and loading of Windows 2000. I checked the BIOS setup to see what the temperatures were going to there and they are normal like they used to be. After rebooting from the computer running Windows 2000 at 52 degrees celcius and then going into the BIOS setup. I can watch the temperature drop down into the 40's like it has always been at in the BIOS except it used to raise to the 40's and now its drops to the 40's. So the temperature in the BIOS setup is still the same. It is just the temperature while in Windows 2000. Has anyone had anything similar happen to them? This makes absolutly no sense to me. Thanks. The only thing that I could think of that could have been causing this was if ACPI was not working properly. I couldn't really find to check whether this is turned on or off but I can find it installed in the device manager and I am not having any problems shutting down the computer. I installed a program called CpuIdle Extreme and it is able to get my temperatures down to where they were with Windows XP. This is a shareware program that expires in 30 days though so this is not a real option for me. I don't want to have this thing on my task bar and let it use resources either. So, for some reason Windows 2000 is not able to let CPU idle like Windows XP does. Hopefully someone knows how to fix this one. Thanks.