I am going to upgrade my HD in my iMac from the stock 250GB to a 400GB. I would like to partition this disc so that I can backup the partitions separately. Ideally, I would like a partition for the OS, one for all Users files and another partition for things like music and videos which will be shared. I envisage using about 250GB for the music and videos. I currently share a single iTunes music library which is located in the Shared User's folder which works fine. But I want to have this on a separate partition. I have an external firewire disc to perform a clone to swap out the internal disc. I just wondered is it really worth partitioning this 400GB beast or just leave it alone with a single partition?