You can download mplayer on your friend's computer.
http://www.mplayerhq.hu/design7/news.html
Download mplayer source and binary codec packages
(Before you compile mplayer you need to unpack the codecs archive and put it
in a directory specified in the README file.
Unfortunately, if you have some dependency problems, it might be a difficult task.
Ideally, you'd get your computer to your friend's house, update your system and install necessary
programs.