Is it a necessity to keep OS( when i am upgrading to X, i am a new mac user and i just got my imac for OSX. I don't have enough software to require OS9 on my imac. If I don't have to keep it how do i remove it, when it's already installed. I remember when i was installing X, it asked me i would like to reformat my hard drive with Hfds(I am not sure if i got it right) What is it???