How do I remove an attached DVD-ROM file from DVD Studio Pro?

How do I permanently remove a file that was once built into a disc image in DVDSP?

I have a project that I frequently use to author DVDs. It has custom menus already created. Each time I author a new DVD, I simply replace the .m2v and .ac3 that are in track 1 (along with changing drop zones, chapter menus, etc). At some point along the way I had also included an attached DVD-ROM file in the disc image. Now I can't seem to get rid of it. Even unchecking the box in the inspector and in the build/format menu, it still shows up on the .img. When I deleted the file from the computer, it failed to build the .img.

Specs: I'm using the 2009 MacPro listed below, but using FCS2 on a Snow Leopard partition of the startup drive.