Seems crazy, but "Method 5" at this website worked for me. (I spent hours trying every other solution I could find.) Basically, requires changing where Windows puts extracted temp files.
https://www.partitionwizard.com/partitionmagic/turbotax-not-installing-working.html
Might seem a bit complicated, but it's actually pretty straightforward. I included the text and diagram below. Good Luck!
Method 5. Change TMP and TEMP Environment Variables
Many people report that they have solved the TurboTax not installing issue by changing TMP and TEMP environment variables. You can also try this method.
- Click on the Search icon and type “environment”.
- Click on Edit the System Environment Variables to open it.
- In the System Propertieswindow> on the Advanced tab, click on the Environment Variables button.
- On the Environment Variableswindow, you will find the TEMP and TMP entries under both the User variables and System variables sections.
- Select each of the four entries and then click on the Edit button.
- Change the Variable value to C:TEMP.
- Click the OK button several times to save changes and close windows.