how do I make a new Index the default?

My problem is my online help is a subset of my original FM document, and all the old index links are showing up in the default index. I've deleted most of those files, but don't know which ones offhand.

I'm new to RoboHelp HTML 7. I've put together a new index (called NewIndex) but don't know how to get RoboHelp to use it. How do I make this one the default?

Please help, this gets put on CD Monday, and I'm baffled!