I can try to answer part of your questions. WMP of course requires codecs. So make sure your codecs are up to date, & make sure your DivX player is up to date. It could be any variation of avi. AVI is simply the outer shell. What's inside could be an ostrich, a penguin, fish or a rabbit. There's so so many avi variations. It could be a divx file, a XviD, 3ivx, Matroska 2, etc. You could also try VLC as a 3rd backup player which plays almost all & has built-in codecs: http://www.videolan.org/vlc/ (choose nearest mirror site)

Any files in red in the incomplete folder means they're no longer being downlded & have lost their relationship with the original source. This might be for a few reasons. You can try resuming some of them. Sometimes you downld a file & it makes 2 copies in the incomplete folder (from different sources.) One will continue downlding & the other will remain stagnant. So make sure you haven't already downlded the same file before. Also if you cancel downlds from the downld window then the accompanying incomplete file 'may' also then turn red. But not necessarily. lol

If you resume a corrupt file it will depend on whether the file was corrupt at the original source or due to some transfer problems. Personally I wouldn't do it. I've had a movie become corrupt at 90+% & I dragged it out of the incomplete folder & it was fine to play. Just missed out on the end credits or something. lol