Pl. try my method to install the driver
( I successfully installed HP Deskjet 670C for Vista, & Win 7) . Eventhough Ur printer is different the method will work.
1) Printer is switched on & connect it to the USB of the Computer.Window will automatically install some generic driver.But the Printer will not work as the driver is not the proper one.
2) Using Control Panel go to Printer & U will see the Icon of the connected printer as Unknown Device . Rt click on it , go to the properties and uninstall the driver.
3) In the Printer window , select ADD PRINTER and follow the instructions. When the Driver selection comes up & Window is not showing your HP Printer in the list , select Window update , for driver download.
For full detail of my method refer Window 7 Forum driver for 660C
I am sure this will work. No need to use compatability mode