ok, so I have a 500 GB external hard drive and i would like to use time machine but i do not need 500 GB worth of backups. when I first start time machine it says that it will erase the hard drive, does it use the entire hard drive for the time machine? If so, is there a way I can partition my hard drive using half for time machine and the other half for regular use? does my question make sense? thanks for the help