What settings can one change (from the defaults) to sacrifice playback quality in hops of gaining a more acceptable (less jerky) playback for a marginal CPU. (Older laptop – not my regular machine.)
That somehow depends on how the move file was made. What format, what codec, etc
Some codecs require a lot of cpu power to display (like HD TV or h.264). There are several players that can use a lot of different settings to enhance playback capability. There are also a lot of players (like Windows Media Player) that do a lot of other stuff next to playing your files.
Try the VLC player for instance. (www.videolan.org) I can play high quality divx and dvd with it on my Celeron 500 system.