I have a cybershot digital camera that does 640 x 480 MPG video, but when I transfer them to PC the files are MUCH darker, and some footage is unusable. When I view them in Windows Media Player and turn up the brightness control they look fine, but I can't find a way to permanently save them in that state.

I've tried encoding them to AVI, but once I do, the brightness/contrast controls no longer work the same way. What should I do to brighten the MPEG files permanently?