My question is - do i have to uninstall everything & reinstall from scratch or is there a simpler way i.e. cut & paste?
You must uninstall and reinstall everything, which is much easier than search for dozen of files in the location is being referenced for.
Also, it's VERY important that, during the last Uninstall (or not necessarily the last one, but you must do it at least once), you reply YES to the question "Do you want to remove the Addon Manager?" which is being made at the end of the Uninstall process.
Doing this, will clear up your previous choice, and allow to freely choose the installation folder again.
