Modifying IFOs




I have a DVD that has all the extras but missing the main movie.
I did this on purpose using CloneDVD.

The problem is that I want to compress it with DVD Shrink but when I try to open it I get the error: Invalid DVD Structure.
Obviously because the IFOs still point to a Title that doesnt exist (the main movie).

So the question is, how can I correct the IFOs so that they dont point to the main movie at all ?

Any help ?