V-Ray installer will automatically uninstall any previous versions.
If you need to manually uninstall V-Ray, make sure that Rhino or V-Ray components are not being used. Go to Windows Start > Control Panel > Programs and Features or Start > All Programs > Chaos Group > V-Ray for Rhino adv > Uninstall V-Ray for Rhino adv
This will start the V-Ray uninstaller. Follow the on-screen instructions to remove V-Ray from your system and restore any files overwritten by the installation.
After the uninstallation is complete you may want to manually delete the C:\ProgramData\ASGVIS\VfR564 folder.