Error 4101: Another instance of setup is already running
Error 4101: Another instance of setup is already running occurs when attempting to install TurboTax for Windows.
This could indicate that more than one copy of an installation program (such as the .NET installer) is running.
To resolve this error, simply restart your computer and then install TurboTax.
If the error persists, restart your computer in Selective Startup mode and attempt to install TurboTax again.