Q: How to wake up from S3 via USB devices within the MS Windows XP SP2?
A:
  1. Jumper setting: Ensure all USB-PWR jumpers are set to enable on your board already.
  2. BIOS setting: Enable the function "Resume by USB from S 3" .
  3. Modify Windows Registry: According to Microsoft you might have to alter your registry:
    http://support.microsoft.com/kb/841858

Use "regedit.exe" to change your Windows Registry settings.
Note the warnings by MS, and backup your registry before proceeding.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\usb
"USBBIOSx"=DWORD:00000000

By doing this, USB devices can be enabled to wake the computer up if you check the "Allow this device to bring the computer out of standby" check box. This check box can be found on the Power Management property page in the Device Manager.