HP have any Vista drivers?
That's how I got mine to work - slightly different problem - 7 installed the scanner Ok, but put the printer in "unknown devices".
I rt clicked the "unknown device" in device manger, selected update drivers , let me choose or whatever it says ( something similar)
and pointed it at the Vista partition "C:\Windows\System32\DriverStore\FileRepository".
It found drivers there and installed them no trouble.