As Tony and Cari note it depends a lot on which printer you have - please
give more details. If you are trying to install the original drivers that
came with the printer you will need to install the proper Vista drivers,
either from those available in the "Add Printer" section or by download from
HP at http://welcome.hp.com/country/us/en/support.html.
I fell into the trap of assuming the OP had the PSC 1315 AIO which does have
drivers for Vista. I guess from his post that he has the Photosmart 1315 which
as you rightly say is not supported. I installed a PSC 1315 AIO some time ago
in Vista without any trouble at a customer's site.