Lost preview of movie files, how to restore?

I do some video editing work in my spare time with a few vids, but I've just had to reinstall windows xp,

When looking in folders I used to be able to see a preview of the video file, it gives you a still picture of the video. I seemed to have somehow turned that off, does anyone know if there is a registry key or something that turns it back on?

I've got the "Thumbnail" tab selected and all my pictures show up but the video clips just come up with a Windows Media Player icon where as before they showed the first frame and I didn't have to search endless for each clip.

I've played around with the folder settings but this makes no difference, I've got the latest Div X codec pack as well.

Any help would be great

if you have installed ffdshow you have to go into the ffdshow video decoder settings and remove 'explorer.exe' from the 'dont use ffdshow in...' bit :) not sure what the exact setting is for divx though

This is the thing, I havent installed anything other than my codecs.

I was playing around with msconfig and some uneeded services but I dont think I disbaled anything that used this.

Is there a service that explorer needs?