Uninstalling FortiClient 6.0.5.xxxx
If you are unable to uninstall the original Forticlient which prevents from install the newest version, Follow these steps:
In FortiClient, go to Settings, then unlock the configuration.In the Windows System Tray, right-click the FortiTray icon, then select Shutdown FortiClient.
Once FortiClient is shutdown, uninstall FortiClient using the Windows Add/Remove Programs application.