XP Can't Use Win7 Connected Printer

I have an HP deskjet 990 printer USB connected to my new Windows 7 desktop and working just fine (with updated x64 drivers).
In the Network & Sharing Center I have:
-Network Discovery ON
-File & Printer Sharing ON
-Public Folder Sharing ON
In the Printer Properties I have:
-Share This Printer ON
-Render Print Jobs on Client Computers ON
When I try to add the printer to an XP Pro laptop and:
-Specify a Network Printer
-Browse for a Printer
-WORKGROUP comes up in the network list with nothing below it; i.e. no printer to choose.
Can anybody help?
(This was working when both computers were running XP Pro)

Thanks, RedBirdDad. The first step did it! The Workgroup name was different on the two machines because Win7 has a different default from XP during install/setup. Made them both MSHOME and printer sprang to life.