How to add HP 64 bit printers for printers that use universal printer driver to server 2003

If you go to your Printer Properties and look on the 'Sharing' tab, you will find a button called "Additional Drivers". Click that. In that dialog you can add drivers for x86_64 and Itanium clients. HP publishes a Universal Driver for 64-bit as well.

In my experience, most HP printers do have model-specific drivers if you look for them.

You need to make sure that the driver versions for the x64 version are identical to those of the currently installed driver. You can't use the 5.5 x64 UPD with the 5.1 x86 UPD. They have to be identical. You also can't mix and match printer-specific drivers with a UPD for the same printer. Again, the drivers must match exactly other than platform architecture.

This isn't a limitation of the HP UPD, you'll run into this for any mixed-arch driver deployment on Windows.