How can I do that in Mac OSX?
I have had this problem - got an HP Deskjet hooked up to my G5-Imac via USB plus some other machines(Macs and PC's) round the house running OS8/&9. Everything shares the same broadband Internet connection - our home network is wired rather than wireless, but the principals are the same.
First off - the help in Mac OSX sucks! You have to do most of the work on the Windows side(and the help there is not much better - hence this thread!)).
1)Put the OSX machine into the same workgroup the PC's are in(usually MSHOME).(The OSX default workgroup is called WORKGROUP). The easiest way to do this is just to rename the OSX workgroup
2)In the printers and faxes pane turn on sharing for the printer you want to share. I had problems until I made the HP the default printer(you can always change this in the application when you want to print elsewhere).
3) Job done - now swap to the windows machine and just follow the steps the others have given.
4)Don't forget to configure your firewall(I'm using XP Pro/SP2) to allow the printer ports 613&515(can'r remember - you might have to add one of these to the OSX firewall exceptions too). Do this first, otherwise you will get 'Access denied' when you try to use the printer.
This works for me in Panther, but trawling macfixit.com shows that others have used different ways to do this.
Also, if you want to share files, the fact that the OSX box is now in the same workgroup means that the instructions given by James et all work fine(just remember that the first time it connects to either a file or printer you'll need to give your SHORT OSX username, not the long one(e.g. Fred Bloggs) that you usually use to login)