From your Macs Sharing preferences pane, make sure that Printer Sharing is enabled.
On your Windows machine, download and install Bonjour for Windows
After installing, click on the Printer Setup Wizard shortcut installed by Bonjour on the Windows desktop
Select your printer from the list of network devices found by Bonjour
Select Generic PostScript Printer (the default) as the printer type
Im not too clear on why you need to use generic postscript driver rather than the native driver, but you do. I tried using the native driver for my Canon i960 but it failed to print. Ive seen several other folks reporting this as well. Its even selected by the Wizard by default. In any case, it works well with full color support and so forth.