That's what I was doing it also, keeping a Windows XP machine running
just to act as a printer server. Now I use the Ubuntu machine for just
about everything. You can change your network setting by right clicking
the network icon on the top of your desktop and selecting edit. Under
IPv4 Settings you can select manual under method and then add then enter
your address, netmask and gateway. Here's a good document on the CUPS
printing.

https://help.ubuntu.com/community/NetworkPrintingFromWinXP