Go to
www.doom9.org.
Click on "The Guides" then
click on "DivX Guides" then
click on "Divx4" then
click on "Gknot" then
Follow the steps shown, Step 0 is installation.
Then under step 1 click the first word "Gknot"
and this takes you to an excellent howto on going from DVD to Divx...when encoding, use the settings in the above post from chris.