If you have DivX that won't play in Media Player try to use DivXFix . Run the divfix.exe in the win32 folder and just open the broken DivX and hit Rebuild Index and after the process it should work perfect.
Or try to use Virtualdub and when open you select File->Open and check Popup extended open options and open the broken DivX . A window appear check Rederive keyframe flags and hit OK.It will take some minutes. Select Video->DirectStreamCopy and Audio->DirectStreamCopy and last save the new DivX, File->Save as avi.
Or try to use Virtualdub 1.4.9 or later and open the broken DivX. Select File->Scan Video stream for errors.Select Video->DirectStreamCopy and Audio->DirectStreamCopy and last save the new DivX, File->Save as avi.