As much as possible avoid uploading raw AVI files in youtube. You need to convert the file into a different format like MPG, WMV or other youtube supported video formats. There's a freeware called DVDVideoSoft for that or you can simply import the AVI file in Windows Movie Maker then do some revisions and save it as WMV. You may also try using other high end video editing software like Vegas, Final Cut Pro, Aftereffects..etc but you need to purchase them.