Hi
Are you using HP OEM Windows 7 ?
(Which was supplied with the HP)
If so it probably reads the HP oem windows key from firmware on the motherboard
And only works on that range of motherboards
This key may well not work with retail windows
Annoyingly the keys for win 7 with sp1 are not compatible for win 7 without any service pack, though a latter version of win 7 sp1 would accept either key
Nirsoft produkey is another keyfinder
Regards
Mike Barnes