^ As said there, all you need is a boot loader. If you plan on installing any Linux distro with Windows, just have Windows installed first and then install the linux distro, it will automatically install GRUB (that's the most common Linux boot loader, dunno of others apart from LILO) and configure it so that you can choose which OS to boot at startup. As for any other OSs, specifics as to how to do this vary... what OSs are you planning on running?