Not able to install Forticlient 4.2.6 - rollback action

Hi All My problem is i am trying to install the latest Forticlient 4.2.6 but the installation cannot complete and rollback. I was using using fine with version 4.2.3. Then i uninstall and try out FC LITE 4.3.3 and then uninstall and to try FC 4.2.6 when i hit the problem The error message is as below " Forticlient Endpoint Security Setup ended prematurely because of an error. Your syste, has not been modified. To install this program at a later time, run Setup Wizard again. Click the Finish button to exit the Setup Wizard" I have disabled the firewall & the AV when doing the installation I even, clean up all " fortinet" from registry (very desperate action) the FCremove.eve doesnt help either regards and hope someone able to help