can you give some more details... like, what happens when you try to install it? does the installer run? do you have a folder for turbo tax in your apps folder in the finder?
i'm not a certified macintosh expert, as i doubt many here are either, but we will certainly try to help you as much as we can
[edit] you might also wish to try out
www.macosx.com which is a mac-specific board whose members might be able to help you out a bit more.