I think I've found a solution to the puzzle. A technician at Staples says the reason the playback from disk stutters is because the DVD RW drive in this computer (hp DVD RW DU8AESH) can't read fast enough to play AVCHD (.mts) files, which are very large video files, without stuttering. It can read and write fast enough to record from other media or copy to other media but it can't read fast enough to play AVCHD files without stopping and starting.