Nope. Nothing I do will show me thumbnails for XAR files. Other filetypes such as JPGs BMPs etc show thumbnails, but not XAR.

Thanks for all your help guys; at least I know that it's possible now. All I have to do is work out what's stopping me from seeing them. I'll see if another prog (IrfanView?) is interfering.

I'll report back with my results.