You should be able to wipe the hard drive and reinstall the OS as a new system, rather than an upgrade. You would lose any other applications unless you have the CDs or license codes to re-install them as well. (You may be able to reinstall your apps from a Time Machine backup, but that does not always work. It's best to reinstall from the original installer file or disk). You will also lose your data files, songs, movies, etc. of course, and will have to reload them from a backup. This procedure will literally erase everything on the hard drive.
There are a couple of procedures online to download the OS installer to a flash drive, which you use to reboot your Mac, erase the hard drive, and reinstall a clean copy of the new OS. I can give you a link if you want to try it.
Or, you will have to return the CD, and use Turbotax Online (the web version) which works from any web connected computer.
The CD has a 60 day satisfaction guarantee from Intuit if the original seller won't take it back.
The Satisfaction Guaranteed policy and claim form are here.
https://ttlc.intuit.com/replies/3301962
