Airport Utility was pre-installed on my iMac (Intel) and I don't know how to use Time Machine with Airport. I want to backup my hard drive and thought that Time Machine would do this. I receive a message to select a Backup Disc. Do I have to partition my hard drive to have the backup on my iMac? Alternately I could purchase an external hard drive with USB 3.0. Would Time Machine detect the USB external drive so that I could select that as the Backup Disc? Are there any cons for Apple wireless hard drives?