Unknown error

Anyone know what is causing this and how to get rid of it, it pops up from time to time and does no appear to affect the system.

This probably happens because the Windows Installer is looking for a cached .msi file (vc_runtimeAdditional_x86.msi) from an older or broken installation package that is no longer on your computer.

If so, some cleaning is needed.
The problem being to identify which package it related to.

You could perhaps search the registry to determine which Visual C++ there's a reference for - here's an example:


and then compare the list you find with what actually appears to be installed and see if there's a difference.

Otherwise if it is related to something needed you could:

- Identify (e.g. by elimination) which installed program needs that instance of Visual C
++ and reinstall it

- Uninstall and Reinstall all Microsoft Visual C++ instances (not the best idea if you have a lot of them!)

Suggests something's not been properly uninstalled or been damaged in some way.

have you run a virus check ? malwarebytes still works?