It is not the responsibility of Microsoft to write drivers for other manufacturer's products but the manufacturer; and in your case it would be HP's to write a new driver for Windows 7 for that model scanjet, which they evidently did not elect to do so - they may believe the product is beyond its life-cycle, possibly something else.
As a possible work-around, if they list a driver for Windows Vista (and the correct bit version, i.e., 32-bit or 64-bit) I'd give it a try (after creating a new restore point). Again, that's what I'd try, proceed at your own risk.
Regards,
chet814