The only way to open a .tax2010 tax return file is with the TurboTax software for 2010. The 2010 software is no longer available, so you would only be able to use it if you already have it installed. If not, you could try the TaxPrinter service at http://www.taxprinter.com/?soft=TurboTax . You send them your .tax2010 file and they send you back a PDF of the tax return. TaxPrinter has no connection with TurboTax.