I have a 60Gbyte Passport, it's fine and works very well on anything I've connected it too with it's own short USB cable.
I have a second 2.5" box with a Toshiba laptop drive I installed and that is very choosey. It came with a cable with a Y connection to 2 USB connectors, so it can get some extra power, it seems the 0.5A available from a USB port is not enough for all 2.5" HDD's. Strangely it works fine with a laptop using a single plug, but not well with desk top systems, then it needs two plugs connected.