Here is a few questions I have about HardDrives I would like to clear up.... 1.) If you clean install Mac OsX several times over the course of say a year, will each new installation be effected by the previous installation before it.. a.k.a old data appearing, programs not entirely erased...? (This seems to be happening to me) 2.) If question number one is true, how do you entirely clean install Mac OsX so that the current installation is not effected by the previous ones?