The older computer I formatted with a retail version of Vista Home Premium last Saturday, and said DURING installation it "validated" using the key off the sticker on the side of the PC cabinet, popped up a dialog today, nearly a week later, and AFTER it had no problems downloading all the updates and Microsoft Security Essentials, saying that the copy of Windows was "invalid"!
So, after my initial "WTF?!?" moment, I call the toll free number in the "Validation" box. The automated system had me read off a set of numbers in the validation box, then gave me a new set of numbers to key in. As of now, it says Windows is "Validated" once again. At least I haven't had to resort to the HP "recovery discs"... yet anyway... trying hard to avoid all that HP "crapware"!