If the movie stop during playback is lack of memory you have only 2 gig memory is your computer if you try to play AVCHD is near impossible because to obtain a smoth playback this neeed at least 8 gig memory and I 7 chip.
Imagine you try to edit the computer cannot calculate your position on timeline if you move on timeline it try to calculate the new position and it cannot do it and jump to any position.
Video need more ressource in memory and computer your computer can do SD (Standard video or standard DVD) I hope that you run at least XP SP3 without a lot of open program. You can check with Ctrl+Alt+Del key to see all opened program and memory to run the computer. Check the bottom screen of the processes tab.