Bob, while there are rare exceptions, generally speaking, OSes are hardware specific. If you have a Windows machine, it's best to stick to Windows. There are such things as Hackintoshes (install Mac software on non Mac hardware), but it's only for the advanced hobbyist.
What version of windows are you using? Do you have the original install disk that came with it? Do you have files on this machine that, if lost, would be catastrophic?