It is possible, but you need to make sure of the following:
- The printer is shared on the Windows computer, and your username has access to the printer share.
- The firewall (if any) on the Windows computer allows for printer sharing.
Then, you go to System Preferences -> Print & Fax ->+->More Printers. Change the first dropdown menu to say "Windows Printing" and the second dropdown menu to your workgroup. Double click on the printer, and log in. If it's XP Home edition, you don't have to log in. Click OK, close everything, and it should work.
It sounds like alot... but most of the work is in Windows.