The specific external drive used is hardware locked if you wanted to use the onscreen interface. This can be bypassed once the PROM has been replaced.

The only advice I would give is that if you can live with a single 1-1.2Gb drive (~200 hours HD/400 Hours SD) then don't use an external drive at all. If either drive fails you are in trouble and by having 2 drives, you double the chance of one of the drives failing.

Peter.