Well, what we really need to know first is what the mac is, if it's Intel based (v 10.5+) then it's as simple as turn on the comp, insert the cd/dvd, boot from it and re-do the partitions during setup.

If it's an older Mac then it means it's running on Motorola hardware (Apple's proprietary) and Windows will need to run on an emulator and the emulator will need to run on the Mac OS.