When making a movie in AVI format, select Microsoft MPEG-4 as the Video Compressor and MPEG Layer-3 as the audio compressor. You will get high quality compression. You can also configure the video compressor in screen 3 of 4 of the Make Movie Wizard.
Make sure that the dimension of the movie is same as the original. Other AVI properties like Frame Rate, Key Frame Rate and Quality also affect the size of the output movie. Keep these settings as close as possible to the original file.
To know more about Compression in AVI, You may read our article on Understanding Compression in AVI:
http://www.deskshare.com/Resources/articles/Compression_AVI.aspx