I tried this program called AVIJoiner. It joined my file but now the joined file isn't even recognizable by MPC or VLC player. And I tried splitting with this program called Ultra AVI Converter. It split the files but when they were joined together it left them with a totally black screen.
Hers two guides if oyu want to know how to do it http://www.afterdawn.com/guides/archive/virtualdub_join_avi.cfm http://www.afterdawn.com/guides/archive/cut_avi_with_virtualdub.cfm