When I first bought my Western Digital Passport drive I had all intentions of putting hundreds of movies on it and plugging it into my USB enabled DVD player that's hooked up to my TV. Unfortunately it didn't work :( The drive draws power through the USB cable, and the LG DVD player I have, doesn't supply enough. I thought that if I bought an external case with it's own power adapter, took the drive out of the Passport and put it in there, it might work. Nope didn't work either, it was still drawing power from the DVD player. Last night my brother said "All you need to do is find the pin in the USB cable that has power and disconnect it." Eureka!
As always you do this at your own risk and I will not be responsible for any damages to your drive, dvd player, or computer. Everything worked fine for me though.
This would also work with a Computer that doesn't have enough power to run a Passport.