If you are planning to use TurboTax Online version to complete your return, Windows Vista is fine to use as long as your computer meet all other requirements below and supports one of the web browsers listed under Windows Vista.
You may not be able to use the TurboTax desktop version unless the administrator rights option works for you. Administrator rights are required to install and run TurboTax on Windows Vista or later. And you can see more on requirements for desktop version here Minimum System Requirements for TurboTax Windows Software
TurboTax Online System Requirements for Tax Year 2017
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