Using turbotax without state forms error 190

I helped my son with his taxes and he purchased the New York state forms.  I want to help him review his federal taxes, and have a copy of his tax file.  However, turbotax won't even let me load the file since I don't have the new york forms on my computer.  I get error 190.  I only want to help him review his federal forms.  How can I load this tax file on my computer without purchasing New York again.