I want to read my old Turbotax returns from 1994 to the present. What can I use to read the files? The old software will not even install on Windows 10.

Do you only have the .tax files?  You didn't save the pdf each year?

you could try the TaxPrinter service to convert a .tax file to pdf at

http://www.taxprinter.com

They might be expensive and it is probably not safe to email tax returns back and forth.  They are not related to Turbo Tax.

I have saved the PDF's since there was an option to do that, but in 1994 you could not do that. 

if you want tax returns going way back, keep a paper copy in your file cabinet.

The oldest return I have is from 1981.

All it's good for is to show how little money you needed to live on in those days. And to  remind me of my stock trading follies.