You can open the folder in which both tax returns are saved, and delete the one you do not need. First save the "good" tax file and use File > Save As to name it something like "2016 Taxes In progress" or something similar so you know not to delete this file.
TurboTax saves your .tax files in the Documents folder by default. If you cannot locate these files, you can search your C Drive for .tax files so you can locate the folder they are in. Please see this link for instructions on how to find files on your computer.