Oops! Sorry I've just reread the post title and saw TOC not "project". If you look for the .HHC file in your project's directory, take a copy of it and name it accordingly. Now providing you are using RoboHelp version 7 or after you can choose which TOC to use when you compile by specifying this in your single source layout. Perhaps even duplicate the layout so you have two, one for each TOC.
Actually, if it's RoboHelp 7 or 8 you can create a duplicate copy of the TOC from inside RoboHelp. The video linked below will show you how it's done.
Helpful and Handy Links
brilliant, exactly what i wanted. wonder why they didnt make that a bit easier....right click, duplicate....
anyways, thank you!