I understand that there can only be one hard drive on an iMac and that the entire drive must be formatted in one file system. In other words, one can't format one partition as HFS+, another as HFS, and other as something else. It would seem to me, then, that one can only run YDL on an iMac if that is the only OS, and that one couldn't dual boot Mac OS X or Mac OS 9 and YDL. Jim O'Reilly