11.7. From Windows.

Printing from a Windows (or presumably, OS/2) client to a Un*x server is directly supported over SMB through the use of the SAMBA package, which also supports file sharing of your Un*x filesystem to Windows clients.

Samba includes fairly complete documentation, and there is a good Samba FAQ which covers it, too. You can either configure a magic filter on the Un*x box and print PostScript to it, or run around installing printer-specific drivers on all the Windows machines and having a queue for them with no filters at all. Relying on the Windows drivers may in some cases produce better output, but is a bit more of an administrative hassle if there are many Windows boxes. So try Postscript first. Modern versions of Samba should support the automagical driver download mechanism offered by Windows NT servers to deal with this problem.