About to clone a 500GB system drive to a new 1TB drive and I want to keep the old C: in the case as a backup drive. I don't want to immediately wipe the old drive till all happy that the new drive is fine and dandy.

Just a little cautious with drive lettering. I intend first booting with only the new drive installed to establish the C: setting on the new drive but after that, will Vista happily assign another letter to the old drive when it is installed (don't want no C: lettering conflict!).