Something Wrong With My Mpegs

Hi, I just bought this brand new digital camera and it records film clips. They save as mpg format and I upload the to my computer to watch them. I can see the perfectly fine only for this one problem. You know how each clip has like a time/duration clock on the bottom right hand of windows media player? Well say I recorded a 30 second clip, when I watch it in windows media player, or actually any player for that matter, the clock stops at like 5 seconds. Or sometimes it'll stop at ten seconds, but it'll stop at a different time with each clip. The reason I want to fix this is because I don't know how long the actual clip is. It'll stop at an early time and the film and audio will still play since its actually longer than what the time says. WHen I try to edit these clips, windows movie maker only allows me to edit the length that goes by the clock so I can only edit about the time that shows on the clip. The rest of the clip doesn't play like it normally does in a video player. Can anyone help? Or do I need to post more information about my problem, if so, then what else Do I need to add?