In a previous post, I showed how to change an .ogv file to a .avi one which is useful is you're going to give the video to a windows user. One problem I faced is that my resolution is too high and after I created the output avi file, it was about 7 MB in size which was too large as an e-mail attachment, you can simply add the parameter "-vf scale=800:600" to reduce the resolution to 800*600, e.g.
mencoder OMPerf.ogv -vf scale=800:600 -ovc xvid -oac mp3lame -xvidencopts pass=1 -o output.avi
OMPerf.ogv is the input file
800*600 is the resolution
output.avi is the output file