There is no controller for brightness control and the screen remains at full brightness by default. Hard on the eyes and the battery as well.
Please help.

Hi there

I take it you have tried the Fn + F8 brightness feature?
Press and hold the Fn key then press the F8 button repeatedly whilst in Windows.

Still not working:
You need to download the "HP Quick Launch Buttons" driver from the following page:

HP Compaq 6730s Notebook PC -  Download drivers and software - HP Business Support Center

Windows 8 is not listed so download the Windows 7 driver.
If you have Win8 32bit download the Win7 32bit
If you have Win8 64bit download the Win7 64bit

If this still doesn't work then try changing the display setting of windows.
Move your mouse to the top right corner of the screen and click.
You should find the brightness icon at the bottom.

Hope this helps...
Grant