from the drivers release notes ... I assume you read them first???
Do not Use Windows Rollback for Graphics Drivers
To reinstall a previous or older NVIDIA graphics driver, do not use the Windows rollback feature. This method will not reliably restore all the previous driver files.
Instead, use the Windows Add and Remove programs to remove the current driver, and then install the older driver using setup.exe.
Uninstalling Drivers Using Device Manager is not Supported
Issue
On all supported versions of Microsoft Windows, uninstalling the NVIDIA driver using the Windows Device Manager may not remove associated files or applications.
Explanation
Microsoft has confirmed that this behavior is by design. If you wish to uninstall the NVIDIA driver, it is recommended that you do so using Add and Remove programs