You need to enable C&Q in the BIOS, install the AMD processor driver.
AMD Processor Driver Version 1.3.2.0053 for Windows XP and Windows Server 2003 (x86 and x64) - Allows the system to automatically adjust the CPU speed, voltage and power combination to match the instantaneous user performance need. This package is a user friendly localized software installation of the driver designed for end-users. This driver supports AMD processors on Windows XP SP2 and Windows Server 2003 SP2 x86 and x64 Editions.
...and you need to set your power management in windows to "minimal power management".