Download the firmware from here
Note 1: If you get "Waiting for device", install drivers properly.
Note 2:The zip will not extract, you have to use it directly without extracting. So don't bother trying to extract the zip, it will always give you error.
Note 3: If using windows 8/8.1/10, make sure to disable driver signature check before installing drivers.
Install fastboot drivers from below if not installed previously..
FastbootDrivers1 or FastbootDrivers2
Download fastboot tools from the attachement, extract it somewhere..
Method 1: pushing the RUU through PC
Now place the above downloaded zip inside the same folder having "fastboot.exe" and rename it to "firmware.zip"
Open command prompt onto the current folder (Shift+Right Click on the folder then select "Open Command Window here")
Boot into fastboot mode (Vol down+ Power then select fastboot)
Now type the commands as given below..
1. fastboot reboot-bootloader
2. fastboot oem lock (If Bootloader is Unlocked previously otherwise skip)
3. fastboot oem rebootRUU
wait for silver htc logo
3. fastboot flash zip firmware.zip
Now some progress bar should appear onto you phone. Wait for it to finish, after that
4. fastboot reboot
Method 2: from the phone itself thanks to @Kellwa
2- Rename the downloaded zip to 0PFJIMG.zip
3- Put the file on sd card and insert it into mobile
4- Reboot into bootloader and it will ask you if you want to update
5- Press VOL UP to say yes