First, Dell printers are just rebadged Lexmark printers, which are barely worth keeping if you get them free.

Second, if you're trying to network a printer for an office, the best thing you can do is invest in a print server device. Depending on where you buy it, and what options you want with it, the price can range from less than $50 to well over $100. Anyway, this device will let you assign an IP address to the printer, and have it's own direct connection to the LAN. Neatly avoiding all the security issues with printer sharing with Windows, as well as many of the headaches.

Of course if you insist on using Windows printer sharing and understand the many drawbacks to this approach, then you might want to make sure you don't have any firewall issues. XP SP2 turns the built-in firewall on by default, and it drops all incoming connections by default. So you'll either need to disable or configure that to allow printer requests. If you don't know how to do this, find someone who does, or get the print server. Better yet, buy a printer that can connect to a 10/100 network directly.