I am a happy TMSR5 user since many years.
I have 5.0.22.28 fully licensed up and running on my Win10/1903 machine.
When I run the 5.2.23.29 installer, I get a "The specified acccount already exists" message, then the installation rolls back & aborts.

I have no clue....Any idea ???

The A/V on this machine is Windows' built-in Windows Security

Dear TMPGEnc,

Please answer this question !
I tried to fill a Support request, but when validating the questionnaire, I allways get "CUDA function has not been entered."

I DON'T KNOW HOW TO REACH YOU NOW TO GET SUPPORT !
I AM A RETURNING PAYING CUTOMER !!!

Same problem here. The update ends with the same error message.

Having exactly the same issue. You'd think they would have fixed it by now.

I've reported the issue to Technical Support.

OK, this was the response from Technical Support:

"The error "The specified account already exists" occurred during installation or uninstallation.

If the error happens, some functions of the Windows installer may not work properly.

Please try the following troubleshooting tool provided by Microsoft.
https://support.microsoft.com/en-us/help/17588/windows-fix-problems-that-block-programs-being-installed-or-removed

If the above download link is not available, please download it from the following link.
https://download1.pegasys-inc.com/download_files//MicrosoftProgram_Install_and_Uninstall.meta.diagcab"

What worked for me was running the MicrosoftProgram_Install_and_Uninstall.meta.diagcab file from the second download link. It scans for problems and then asks 'Are you having a problem installing or uninstalling a problem ?'. I chose 'uninstalling'. It then checks the registry and gives a list of programs to choose from. Select TMPGenc MPEG Smart Renderer 5 on the list. It then asks 'Uninstall and clean-up ?'. Select 'Yes, try uninstall'. It then fixed the problem and I was able to install version 5.2.23.29 successfully.

Hope that helps others.

@WorBry

That worked for me too, thanks for sharing !