If you don't want to complicate and your OS is Windows, then just:
- install HTC fastboot drivers
- enable USB debugging mode
- download latest radio image
- extract radio image
- start Andriod flasher
- chose Radio and select Radio image
- then wait till procedure is finished

Chce to nějaké HTC fastboot drivers. Nevím, neznám, odkážu vás na hledání v googlu. Sám to na svém HTC zkoušet nebudu.