I wouldn't like to advise you that most programs will run on an external drive, or that it's a particularly good idea. Some programs may require to be on the same drive as Windows, or if the external drive became disconnected while programs were running, this may also cause problems. You could probably get away with it with programs like Firefox, or a non-Windows mail client, such as Thunderbird, and games would probably be OK too, but I would be cautious with anything essential, Kaz.