Vaio VPCs13a7e and LCD brightness

I have a Sony Vaio VPCs13a7e.
I changed hard disk, and reinstalled Windows 7 64 bit from a DVD, but now I'm not able to increase brightness of LCD.
The LCD brightness is the lowest, even if I installed Intel Graphic Driver and set it as maximum.
When I boot the laptop, I get an higher brighness for a while...when Windows 7 is ready to be used, the brightness becomes very low.
I did not install any Vaio's suggested program from Vaio VPCS13a7e web site.
How can I increase brightness?
Thank you