How can I update the fastboot driver for my Sony Xperia device I Need to unlock the bootloader of my Sony xperia m2 dual. It's currently in stock. As soon as I connected my device in fastboot mode by pressing volume up button and connecting the USB cable my device illuminates with blue light which indicates that the device is connected in fastboot mode  When I tried to update the fastboot driver by right clicking the s1 Boot fastboot and clicking the update driver option and by selecting the browser my computer option and when I select the usb-driver from google folder , it's showing error that Windows found the driver but encountered an error while installing the driver. Its also showing error that the hash for the file is not presented at the specified location or the file is appear to be victim of tampering.
My system is
Lenovo IdeaPad 300 with Windows 10 64 bit 
My device is Sony xperia m2 dual.
Kindly help me friends.,
Thank you.
Use the fastboot drivers bundled with Flashtool.

Additionally, those drivers aren't properly signed. Disable Windows driver signature enforcement as shown here, reboot, then install the driver. Note that you are also advised to turn it back on after you're done.