Completely uninstall the printer and all its software (Control Panel - add/remove programs in Win XP). If you have a Windows Vista or Windows 7 computer, double click on System in Control Panel and see if it's 32 or 64 bit. It'll be in there somewhere!

If you are using the CD to reinstall, don't. Go to the website: http://www8.hp.com/us/en/support-drivers.html Type in HP Inkjet (model number), click Search, then choose what operating system you are using - Windows XP, Windows 7 etc. From Vista onwards there were 32 bit and 64 bit systems.

Download and install. If a window pops up asking if you want HP to look for updates, click Yes.

Hope this helps.