In the Create Distribution Kit dialog, you will have to create a new file group for the .inf file generated by the DDW. Toward the bottom of the dialog, hit the "Add Group..." button and give it whatever name you like. Then browse to the .inf file to add it to your new group. You will need to change the "Group Destination" for the group to "Windows Directory", then check the "Relative Path" box and put "inf" as the relative path (aka subdirectory). That's all there is to it.
Hope that helps.
Mert A.
National Instruments