I'm trying to burn videos onto DVD disks. Most of the files are .avi but some are .mkv or .iso. I've tried burning them using DeVeDe and Windows DVD maker (Windows 7) onto either Verbatim DVD-R's or mpm DVD-R's. Whenever I go to play the disks in my DVD player (Sony DVP-SR200P) it won't load, it spins but it's stuck on the 'loading' process. It says on the DVD player itself that DVD-R playback is supported so what am I doing wrong?