I've downloaded numerous AVI format dvds to play on my Real Player and all of them have no picture. They do have very clear sound but the screen is black. I've tried to play it on my Windows media player as well with the same results. Please help! I can't figure out whats wrong...

CODECs is the word that you're missing. Might I recommend you get a backup player with in-built codecs such as VLC (not a pretty player but it does the job) which will play all sorts, & dvd's & vcd's & online streaming of audio & video. Get it here: http://www.videolan.org/vlc/ (choose nearest mirror site)

For your other players, I'd suggest GSpot which will identify which codec you need to get. See CODECs list and alternate players for Movies