My '07 MBP has developed several problems and I'm loath to put much money in it. (first and foremost it has a power system problem that only allows it to run for 5-10min on battery so it isn't really portable anymore.) I think the internal HD is slowly failing and last night I had to repair it. Can I buy an external drive and use it to boot and run apps? For the same price as an internal I can get more space and won't have to pay anyone to install. Once the laptop gives up the ghost I can use the drive with another machine. (This is my second machine - the first is a new MBP retina) Speed on Firewire 2 wouldn't be too bad would it?