windows 7 - Adjust screen brightness hotkeys not working in Vaio laptop

I formatted my Vaio VPCEA37FL laptop and later I installed a clean version of Windows 7.

The problem is, adjust screen brightness hotkeys do not work anymore. I have installed every driver from Sony support website that I think it could be related, but no luck. I contacted Sony support, but they told me it is necessary to modify the registry and they want to charge me 80 dollars (it includes a computer scan).

So, does anybody know what do I need to do to fix it? Do I really need to modify the registry?

Thanks.