Hi

For the brightness control buttons to work on the keyboard we need an application installed.

The QuickSet    Application would enable the use of function keys.

However this application supports both the 32bit and 64bit versions of Vista and Win7, Windows XP is not supported.

To change the brightness level when the laptop is on battery we need to look into the power management option in the control panel, the default windows setting is to keep the brightness lesser when on battery to add a couple of more minutes to the battery backup irrespective of the charge on the battery.

The changes can be done in power management

Thank you for answer.
I looked in detail all the options on power management window, but there's nothing about brightness adjustments.
I'm still looking for help.

My apologies, please follow these steps

1. Navigate to the "Control Panel" from the Windows XP "Start" menu.
2. Choose "Appearance and Themes" when prompted in the "Category View" panel. If you're in "Classic View," choose the "Display" icon
3. Select the "Settings" tab from the Display Properties window.
4. Select the "Advanced" button on the bottom of the window. This will take you to your monitor's properties.
5. Choose the "Color" tab if using a monitors with an ATI graphics card.
6. Select the brightness scale and push or pull it until you are satisfied with the brightness of your screen.
7. Press "OK" to set your brightness.

Thanks for trying to help me.
I don't have ATI card. I have brightness settings on "Intel HD graphics" software, but they don't change screen brightness via hardware, that's only software changes. It's really easy to notice that. I'm still looking for solution.

PS
I also tried to change "power plans", but still without success. Seem like screen brightness is under automatic control when laptop is using batteries (very low brightness) and I'm not able to take control over screen brightness of my laptop.