Run the windows memory diagnostic tool http://www.softpedia.com/get/Tweak/Memo ... stic.shtml
, or use http://www.memtest86.com/
As for the video errors, try uninstalling all your codecs and start from scratch with Kopei's xvid codec (supports divx as well) http://www.xvidmovies.com/codec/
If you still have issues you could try the Gordian Knot codec pack.