I should forget trying to run mac os on a pc since it isn`t that useful atm, as for Linux, either download a live cd, or download Suse Linux, imo that is the simplest to use and most complete Linux, the others being limited in some way, download 9.2 rather than 9.3 since 9.3 is problematic atm, defragment your windows drive before you start and then set your BIOS to boot from the CD drive if it does not already, then just insert the cd, reboot and accept the default installation, it will take some space off windows and install the bootloader and linux to this space, then you can try it out, if you then want to remove it you will need your windows install disk, otherwise you will be stuck with the bootloader, so make sure that is available before you start.
why do they say Aliens are gonna be friendly?, surely the agressive ones wipe out the peaceloving ones, so all you have left out there are crazed flesh eating interstellar monsters.