What you want to look for is a "printer driver." (The driver is a piece of software that will tell your computer the printer exists and how to use it.

) What you need to download is a file to your harddrive (or to a disk, it doesn't matter) and run it. It will set up everything for you.
To make things a bit easier, here is the link for the Deskjet 648
c (That's what you have, right?):
http://h20015.www2.hp.com/en/softwar...191&sw_lang=en
Go there and click your operating system, then just click the driver link to download it. Run the file once and your printer will be working in no time.
hope this helps...
~psi42