I got a workstation with a downgraded Vist64 biz to XP. I then a few months later upgraded to Vista64 Biz. Got fed up. Formatted my harddrive and installed XP, but now I get invailed key for my XP reinstall....
How did you downgrade to XP? Did you have a proper XP key to downgrade to? Did you do a Vista upgrade from XP? If you upgraded to Vista, Microsoft revokes your XP key. You need to call Microsoft and get the XP key reinstated and your Vista key revoked.