When downloading a movie in the XVID format after it has been downloades, when i go to open it, I get a message that I can not render the file. how do i correct this problem, so i will not experience this in the future.
Download K-Lite codec pack. It will allow you be able to play a great variety of video/audio formats. http://www.free-codecs.com/download/K_Lite_Codec_Pack.htm
Make sure you use MediaPlayerClassic that comes with K-Lite to play all your video files, it will allow you to play 98% of video formats out there.
VLC (VideoLAN Player) is also a good alternative if you can't install KLite (for example, if you don't have administrator rights on the machine you're installing on).
VLC is probably the most compatible and format-friendly player out there but it's pretty bare if you ask me.. it doesn't support a lot of the higher quality renderers and audio mixers like MPC does, usually giving inferior quality. But if nothing else works use it..