Cannot uninstall Quest Installer, giving the error "The Quest Installer has detected that the fol (4228906)

When trying to uninstall the Quest Installer, it notes that some products are still left on the system.

The Quest Installer has detected that the following Quest products managed by the Quest Installer are still installed on your machine:
Knowledge Xpert Oracle Common
Quest SQL Optimizer for Oracle Common
To proceed with uninstalling the Quest Installer, you must first uninstall those Quest products.

But these products cannot be found in the Quest Installer itself nor in Add/Remove programs. How do I remove these fully?

WORKAROUND 1:
Reinstall the same versions of the application noted by Quest Installers error. Then reinstall the application again using Quest Installer.

In this case, reinstall Knowledge Xpert and Optimizer

WORKAROUND 2:
Download and install Microsoft Fit It tool. Use this to remove and left over applications listed.

Please refer to Knowledge Article 54910

https://support.quest.com/SolutionDetail.aspx?id=SOL54910&pr=