for some reason, when i play certain .mov (or quick time movie) files, my computer will slow down alot, going at like 1 frame per 10 seconds, lol

its annoying and i have to close the box (when i can eventaully get my cursor on the close box -_-) , and ya...
i think it might have somthign to do with my audio, cause when i play certain ones, it says an audio jack has been unplugged or plugged in and starts opening a little menu, and thats uaully when it lags. I already installed the latest drivers, but it didnt help...
anyone know what is causing this to happen? btw, my audio is Realtek HD Audio if u wanna know that.