My brightness system does not working

Please visit the manufacturer's website to download the drivers for your device. You can use google to find the manufacturer's website if you do not know it. In the support section download the drivers for your specific make and model of the device for your version of Windows.

Note: If the manufacturer only lists drivers for Windows XP and not for Windows Vista or Windows 7, that means the device is unsupported or incompatible with the unlisted operating systems.

If you do NOT know the make & model of your device you can Search by Vendor / Device code as shown in device manager.
In the device manager, for the device you need driver for, Right click properties for the device, go in details for the device driver.
You will see a code like per example VEN_8086&DEV_27D8&SUBSYS...

The VEN code means vendor and the DEV code means device: in this case the vendor is 8086 and the device is 27D8.

Once you have the two codes, go to www.pcidatabase.com.
Enter the two codes and you should get the name of your hardware. From there you can search for a driver download for your hardware.