VLC Media Player--from Videolan.org--is a free, open-source video player and "transcoder" capable of converting to and from over a dozen file types, including a DVD's transport stream (a DVD's main video file contents). You can convert your DVD to a number of formats, including AVI, as long as you make sure to enter the ".avi" file extension in your output file name when you save your video. Please allow several minutes to several hours for DVD conversions to complete.
Launch VLC Media Player and insert your DVD into your computer's disc drive.
Click the "Media" button at the top of VLC's taskbar and select the "Convert/Save" option. (You may also press "Ctrl+R" on your keyboard as a shortcut.)
Check off the "DVD" button in the "Open Media" window. Make sure your "Disc Device" is directed to the disc drive containing your DVD.
Click the "Convert/Save" button at the bottom of the screen.
Press the "Browse" destination file button. Choose a folder on your hard drive to save your converted movie to.
Name your file. Be sure to include the ".avi" file extension. (See Tips)
Choose the "Containers..." option from the "Save As Type" field and click "Save" to enter the "Convert" menu.
Choose one of the "DivX" settings from the "Profile" drop-down menu and click "Start." You can track your DVD's conversion process in the new VLC window that appears.
If inputting the ".avi" file extension does not work, try using the ".mp4" file extension and selecting a "DivX" option from the "Profile" drop-down menu in the "Convert" menu. (AVIs are based on MPEG-4 compression standards, and using a DivX codec will mimic the proper AVI settings.)
Since AVIs are generally of lesser quality than DVD transport streams, you may lose some video quality during conversion.