In these situations the only thing you can do is perform a system repair which will factory reset your device and also means that any and all data will be erased - Use either PCC or SUS found here - For PCC unplug your phone from the Pc and fully switch it off - Start PCC select Support zone then Update my phone/tablet then in Blue select Repair my phone/tablet and follow the instructions - Remember that when prompted hold volume down and connect your USB cable - Your phone should be switched off - In some circumstances you may need to perform this twice as the 1st time will install the Flash driver
