Apple is still relatively new to me, and I'm looking to backup my new MBP. I already own an external HD (with stuff on it) and when I connect it to use Time Machine, it says I have to format the extHD first. Does this mean I'll lose all that I have on it? If so, that's okay, I can always retrieve it from my PC, but once I select the extHD to use with TIme Machine on my MBP, does that mean I can't use it anymore to throw stuff into it from my PC? In other words, does it become solely dedicated to the MBP to use with Time Machine? In general, can I still add stuff to the HD separate from Time Machine (dragging and dropping it in, for example)? Would I have to partition the extHD? Appreciate it if anyone who can clarify.