I burnt the disc with Nero and it said Burn Successfully at the end. But when I tried to play back the video, Windows took a long time to try to read the files and it failed at the end. It seems that it only happens on .avi (divx format). Does anyone know why and how to resolve? By the way, I don't have this problem before until recently.

Did windows media player give you an error message? If so you can look it up on Google. If the burn finished sucessfully I doubt it's a problem with the file itself although you can confirm this by copying the file to your desktop and trying to play it from there. If you still have trouble, try downloading the Media Player Classic at: http://www.divx-digest.com/software/media_player_classic.html And it wouldn't hurt to update your codecs with the Nimo Codec pack: http://www.divx-digest.com/software/nimo_pack.html

Oh, I forgot to note that when the files are on PC, there is no problem whatsoever to play with WMP. I also forgot to mention that I cannot even copy the problematic files back to PC from the DVDR. Thanks.