If you are looking to save disk space and speed up your edit while working on an HD job, you can always capture your footage and edit in DV mode (or any number of the new Pro Res formats) and once you are happy with the edit, convert your whole project back to HD using Media Manager.
Simply save your final Sequence in Media Manager with 'Create Offline' set to your HD settings. Obviously before you can do that you will need to recapture all your footage in HD!
note the format is set to HDTV 720p hereThis brings up a good point. If you shot on tape: label your tapes correctly and don't forget to change the reel number each time you Log & Capture your footage! This is essential to a smooth job. If you shot on P2, well you will need to back that baby up-- probably twice for safety! (So who says P2s save time and space? One little mini-dv tape vs. a P2 card + a laptop + a hard drive + another hard drive + power supply. Oh well! )
The number one problem faced by most newbies is: "where is my footage?"
More strategies to deal with that in another post.