I know what are you wrong, most home DVD player only recognize the standard video DVD which isn't single video file, it is a group file, include VOB, IFO and BUP files. some special DVD player can play avi video files on disc, such as divx certified DVD player(your friends dvd player), so if you want to convert and burn any movies to DVD, and can play well on most home DVD player, you should use the right software to burn standard video DVD from your movies, there is an easy way and the better choice, you can try RZ DVD Creator, it can create/burn standard video DVD from any movies, it can burn long movies into one DVD, it can burn multiple movies into one DVD, it can auto fit the size, it can directly convert and burn any movies to video DVD(DVD+R, DVD-R, DVD-RW, DVD+RW, DVD-R DL, DVD+R DL, etc), such as avi to DVD, etc.
RZ DVD Creator also can create Divx/Xvid AVI Video DVD from any movies.
Yahoo or google search and download "RZ DVD Creator", work well, most functionality, easy to use, hope it can help you.