Download Perfect Flash tool by WMSHUA. Download an ftf file for the latest version.
Open the flash tool.
Now press the power and volume down button together and hold them till the red light blinks again. Then leave the power button while still holding the volume down button. Perfect flash will detect your device.
Now go to flash option and select the downloaded ftf file. Then click on flash.
The phone will start updating and it might be slow. Once it reaches 97%, From 97% to 98% will take bout 20 mins but don't unplug the device.
Once the flash finishes, remove the usb and turn on your device. The first boot will take time but now you have your phone back.
I recommend using this firmware:
http://www.gizmobolt.com/community/thread/download-xperia-c-16-0-b-2-16-firmware-ftf/