|the problem might not be the camera, but the fact that you dont have the programs to play those file types.|
try downloading videolan (vlc player) it plays pretty much anything, and make sure you have the latest drivers for your camera installed as well.
as for a camera, i recently bought a samsung 14mp, cant remember the model, but it's a fantastic camera for its cost...£140
Windows 7 x64
Intel® Core™2 Duo CPU E8500 @ 4.1GHz
ATI Radeon HD4870
8GB OCZ Platinum 1066
2x Samsung 1TB Spinpoint F1