1. Fully charge your S9.
2. Connect your S9 to PC (while connecting your data cable,power on your S9 until the LED goes grey.) The timing should be exact in connecting to PC and pressing the power on key.
3. Install the driver.
4. See your firmware version of S9 just for safety.
5. Flash with firmware of S9-HD.
The advantages by flashing to S9-HD :
1. S9 becomes into S9-HD.
2. When you are calling with the headset,the sound comes stereo. In S9 it's just mono.
3. SRS WOW mode.
Only works with original S9 to know if they are original, enter HERE