Vista product key suddenly invalid???

hi, i went to go on my laptop last night and it loaded up as normal, i put my password in to get on my account and it said welcome as normal on the screen. then a window popped up saqying..."the windows vista home premium product key you typed is invalid for activation" it then gives me three options..
"access your computer with reduced functionality" - it just puts me straight onto the internet which i cant use because i cant load my dongle up.
"type a different product key" why would i have a different product key?
"contact hewlett packard to help resolve this problem" which again puts me straight to an internet browser.

i can log on in safe mode which i have done and ran a system restore. this did nothing.
i would happily enter my product key agin but i cannot find the disk with it on and the sticker on the bottom of my laptop is barely visible, i can make out all but 3-4 digits.
has anybody got any idea whats going on and what i can do to solve this?
thanks in advance

Without giving a long wordy answer as to all the reasons this can happen etc. Try to activate by phone
Activate Windows 7 by Phone - Windows 7 Forums
If the number does not work a rep will come on the line, you can explain and all will be good again.
One possible reason is that you activated too many times and they are becoming concerned. Dont worry, if the key is valid you will get activated
And yes, it works for Vista, too.