mp4 is the best format out of those mentioned. But it is newish & some people do not have the codecs for them. mpg generally refers to mpeg 1 or 2 which are earlier mpeg formats. AVI is not a format per se, it is a containor. The actual video & audio format within could be anything from mpeg 1,2 (perhaps even mpg3 for audio) or 4, divx, etc.
This will give you some tips:
Movie download issues (click on blue link) _ (2nd last post has information on best video formats.)
For playback problems, it is usually a lack of having the correct CODEC to play the particular video or audio within the video. Either updating your codec pac or removing the one you have & getting a decent pack. Should not have more than one codec pack as it can cause clashes & problems.
We usually recommend getting
VLC player as it has codecs builts inside & is generally very reliable. Get it even if just as a back up player.
CODECs list for Movies/Audio/ Alternate players
To change default video player, see
Setting Default video app. Basically the process is ... right-click each type of video file & choose open with such n such player, & tick the option to always open that type of file with that player. You will need to repeat this process for each video format such as mpg, mp4, avi, etc.
January 25th, 2009
Cant watch my downloaded Movies :( 
Linear Mode
