There are about 5 videos i need to put on my site. the source of the video is asking me what format i want them in. the information i've found goes as follows:

AVI - very common, windows only (for the most part), most browsers
Windows Media (wmv) - Windows only unless you download a plug in.
MPEG - Most popular, cross platform
QuickTime - Need plugin for windows
RealVideo - streaming video
Flash (shockwave) - need plugin but preinstalled with most recent netscape and i.e.

My questions are:
1. If MPEG does it all without a plugin, why bother with any of the others?
2. Under what circumstances would i need to look into a video server as opposed to just posting the file?
3. Last i heard AVI was rather archaic, is this true?

thank you for your help.

Flash would probably be the easiest to work with and most people will be able to use it. I guess it really depends on how you wish to deliver them though, do you want them embedded in the page for viewing or do you want people to download them before watching?