BC, have you tried downloading the 5550 or 7350 XP drivers from HP's website? I know those folders do have .inf files in them.
Also, this worked for me when I was setting up networked printers/photocopiers at work:
Goto Add a printer, select Local printer attached to this computer, then deselect the automatically install button, click on the Create new port button, and select standard TCP/IP port. For the next part, it is going to ask you for printer name or IP address. If you have assigned an IP to the printer, then great, if not, you need to find out the printer name, which is a string of letters and numbers. I think you can get it through printing a test page, but you can for sure get it if you access the printer over the network via a web browser: just find out the current IP it is using and enter that into the browser. Anyway, once you have that information and plug it in, windows will again ask you for drivers. Why this will work over the Add Network Printer menu, I don't know, it just doest sometimes. Of course, my experience with this is in XP, so the point could be moot....