Before I got around to trying my solution, Khundon was experiencing a similar problem. Buksida suggested:
andInstead of installing the wads of junk that comes on the HP CD just install the drivers alone, to do this plug the USB printer in, turn it on and Windows will prompt you for the driver, let it search the CD drive and it should find and install only the driver automatically.
Trusting his judgement rather than mine, I went with Buksida's suggestion first. Thank you very much BuksiVista should actually have the drivers for most of today's printers built in, HP instruct you to use their CD in order for them to install the world of shite software that comes with the device!

All but 2 of the drivers were already available in Vista. I then inserted the disk and the other 2 were downloaded. At this point the rest of the rubbish on the disk tried to download - I simply pressed the cancel button, and removed the disk. My friend now has a perfectly working printer.