I'm a new Mac user and I plan on doing some video and photo editing. Nothing professional, simply working with vacation photos and video. I plan on purchasing an HD camcorder later this year to replace my current one. My iMac has a 1TB internal drive and I plan on using a 1TB GTech drive for back-up (getting some help on this in another forum). Would it be beneficial to use a scratch disk for editing? Any other tips for a newcomer to both the Mac and to video editing are greatly appreciated. Thanks.