I have Windows XP Pro SP2 installed in my rig and when I shut it down, the CPU and PSU fans remain powered while everything else has powered down. The problem remains even when I use the power button to turn off the PC, which forces me to use the off switch on the back of the PSU.

I have also flashed my BIOS and downloaded all Microsoft Updates and device drivers for my system with no success. I then saw that there was a Microsoft hotfix for AMD Dual-core systems and installed that before installing the AMD Dual-core optimizer software. No success either. For reference purposes, here is the link describing the MS hotfix: http://support.microsoft.com/kb/896256

I have checked device manager and windows is properly detecting my PC as an APCI compliant Multiprocessor system hardware wise and BIOS wise. Because of this, I cannot enable advanced power management in "Power Options" in the Control Panel. APCI is enabled in the BIOS.

One side issue which I should also mention is that when I choose to put my system in Standby mode, it defaults to the S1 power state even though I have enabled S3 Suspend to RAM mode in the Bios. I'm not sure if this is related to the shutdown problem or not.

I am fairly positive that Windows is the cause of this problem because when I force XP to install using the Standard PC Hardware Abstraction Layer (HAL), I can enable Advanced Power Management in "Power Options" in the Control Panel and the system will then shut down with no issues. I, however, do not want to use this as a solution because I won't be able to realize any performance benefits from using a Dual-core processor.

I have also tried all of the shutdown troubleshooting tips for XP found at: http://www.aumha.org

Thank you all in advance for any help or insight.