Configure your OEM notebook or desktop correctly in Windows XP to support Dual Cores (regardless if its Intel or AMD based)

Make sure that the pre-installed OS (Windows XP w/ Service Pack 2) was correctly modified to fully support your dual core CPU.

The performance of your multitasking and games (ex. BF2, Oblivion, etc) would be a lil F'ed Up if the dual cores are not both being utilized because the setting for your Windows isnt set correctly. This hotfix is for those that want the most out of their Dual Cores. If you are just a casual PC user, this hotfix might not do anything for you. But if you multitask and game, you definitely see an increase in performance. As well as if you do Professional Audio editing and Video editing, this will also help you greatly.

- Windows XP (Home, Pro, MCE) with Service Pack 2 (even when using Apple Bootcamp, NOT Virtual PC)
- Any system (desktop or notebook [even Apple's MacBook's]) with multi-cores, multi-processors, multi-logical processors (Hyper-Threading)
---- Intel: Pentium 4 w/ HT, Pentium D, Core Duo, Core 2 Duo, Dual Core Xeons
---- AMD: Athlon 64 X2, Turion 64 X2, Dual Core Opterons

1) (for Intel CPUs) Check to see if the mandatory Windows XP Hotfix Patch: KB896256 (NOT automatically downloaded with Windows Update) is installed.
if not download KB896256 XP patch and install it.

1) (for AMD CPUs) Check to see if the mandatory Windows XP Hotfix Patch: KB896256 (NOT automatically downloaded with Windows Update) and the AMD CPU drivers are installed.
if not download KB896256 XP patch, AMD CPU Driver and install them. (for AMD Dual Core Optimizer info read Note 2)
Note 1: Only install the AMD Driver if you have an AMD CPU.
Note 2: The AMD Dual-Core Optimizer was AMD's answer to Microsoft's Multi-Core fix... originally, to get the hotfix, one would have to email Microsoft to get it... screw that. Therefore, AMD released their Optimizer to give the public (with AMD CPUs) a way to utilize both cores. If you install the AMD Optimizer and it works without problems, then you would NOT have to install the the WinXP hotfix.
BSOD's (Blue Screens of Death).... If you own a Clevo D900K (A.K.A. Sager 9750, Alienware Aurora m7700, etc) notebook, DO NOT install the AMD Dual Core Optimizer... incompatible. So if you experience BSODs (on any computer) from the AMD Optimizer, then go into Safe Mode and uninstall it. You will still have optimized dual core as long as you do the rest of the guide.

UPDATE: Windows XP Hotfix KB896256 Version 4 (From Microsoft)

2) go to Start Menu > Run. Type REGEDIT and press enter.

The registry location: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Session Manager should have a key named Throttle there, if not make it by right clicking, point at New > Key... name it Throttle.

3) (Still in registry) Inside Throttle key: should be a DWORD called PerfEnablePackageIdle with the value of 1. If not there, right click, point to New > DWORD... name it PerfEnablePackageIdle.
*** Note: You should type 1 in the Value data box to enable the performance state policy behavior (increases performance)

4) Quit Registry.