BTW: This is not even an hack as far as I am concerned but if you have a "Legit" Windows Install that is giving you problem with the WGA... Open up the Windows Updater
Go to Tools, Manage Add Ons, Disable Windows Genuine Advantage..
BINGO!!!! Your Windows Update will work as before....
I had to do this on several Dells fresh out of the box.
Easier than calling M$ and waiting a hour on hold.