Microsoft just went live with their new Windows validation tool.
Called Windows Genuine Advantage Validation Tool (KB892130)
"The Windows Genuine Advantage Validation Tool enables you to verify that your copy of Microsoft Windows is genuine. The tool validates your Windows installation by checking Windows Product Identification and Product Activation status. After you install this item, you may have to restart your computer. Once you have installed this item, it cannot be removed."
So, if you're using a pirated copy of Windows, watch out.