I've tried restarting the computer, no joy. I've spent a lot of time trying to find tech support, no luck there either. I'm feeling pretty desperate.
Do you get a specific error message when trying to open TurboTax Desktop?
Here's some things to try:
How to Turn Off Anti-Virus Programs
Then restart your computer and try opening TurboTax.
Here's more for when TurboTax won't open:
Right-click your taskbar and select Task manager.
If that didn't work, try one of these options:
Run the Windows System File Checker, then try installing/updating again.
Re-register Windows Installer:
Start the Windows Installer Service: