From the MacOS X Help Menu:
Sharing your printer with Windows users
You can let Windows computers on your local network use any printer connected to your computer.
If the Windows users install Bonjour for Windows, you can share your printer with them using Bonjour. To share a printer, open the Print & Fax preferences, then click sharing. Select the option to share printers and select the printers you want to share. Use the Bonjour Printer Wizard on the Windows computer to set up to print to your printer.
Otherwise you can share your printer with Windows users by using SMB/CIFS, as described below.
To share your printer with Windows users by using SMB/CIFS:
1. In Print & Fax preferences, click Sharing.
2. Select the "Share these printers with other computers" checkbox, and then select the printers you wish to share.
3. Click Show All, click Sharing, and then click Services.
4. Select the Windows Sharing checkbox.
To print to your printer using SMB/CIFS, Windows users must configure an SMB/CIFS network printer and use the Postscript printer driver, even if the printer isn't a Postscript printer. Your Mac will translate the Postscript code into code the printer can understand. Have the Windows users see their Windows documentation for information on adding a network printer.
WIndows users printing via SMB/CIFS do not see any location information you may have entered for your printer.
Documents waiting to print on printers you're sharing are stored on your hard disk. (That is, your computer hosts the queue for the printer.)
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Print & Fax preferences