You have not said it you've set up networking for the 2 machines. If you're hardwiring the machines, you'll probably need an ethernet "crossover" cable at the least. Mac to Mac can use a standard ethernet wire, but I don't know about the PC.
You can also buy a cheap ethernet switch and plug standard ethernet cables into that.
If you have wireless on the PC, You can turn on the Mac and have airport search for that network. That usually works pretty simply.
Make sure that, under Apple menu/System preferences/sharing/services you enable Windows sharing. Check the firewall setting to make sure that the windows port is enabled (it should be after enabling windows sharing on services.
Make sure both the pc and printer are on. Then go to system prefs/print & fax and click Add. Pick Windows printer from drop down menu. You'll probably be using network neigborhood from the lower drop down menu, but it might be workgroup - might take a bit of fiddling here. See if the printer shows up. Then hit add.
If you have no reason to network the machines other than printing and don't already own the necessary hardware, you might find it cheaper to just buy another of your hp printers - it it's inexpensive.
Using OSX 10.3.9 on a G4