Answer:
in windows instalation time u will get option where to install window???
keep 2 differant drives is more eassy. u can install windows like this........
than when u start ur pc, u will get option to accept which windows u want to start...but u might have just 5 second to select the option... so be fast.....if u install 2 differant windows like xp, vista..... option will be more eassier to select vista or xp. otherwise option will be xp or xp???