device to play stored movies

This could be a very silly question however I am not too good with the knowledge of different electronic devices out there and hence thought to post the question at RFD :)

I am looking for a device that I can connect to either PS3 or TV(I have HDTV - but no usb slot) and play my stored music and movies. I have a collection of downloaded movies but at the moment on my laptop/external hard drive. Not all movies play through PS3. I want this device to keep connected with my PS3 or TV so that I do not have to remove it all the time.

Any advice is appreciated.

Thank you
NJ