Choppy video playback and no audio

I'm using an old 2008 aluminium macbook, upgraded to mountain lion 10.8.5. The video playback is choppy on iTunes and literally every video player like vlc and quicktime player. There is also no audio from the internal speakers, I've tested videos and on iTunes, there's no sound even when I increase/decrease the volume. Any suggestions on what I can/should do to fix this?