Windows 7 laptop brightness problem

[fender62]

i have a samsung NP-R540-JT02ES laptop the hardrive failed so i put a new one in and installed
Windows 7 ultimate then let windows update everything etc plus i downloaded some drivers from samsung for my model, when i boot without the power cord connected the brightness is always half until i put in the power cord then it goes full brightness, the battery is fully charged
in device manager power options there's a brightness slider, it makes no difference if i slide them
nothing happens with the brightness, basically id like the laptop to remeber my brightness settings
but it will not, iv have reinstalled a few times trying various drivers settings etc makes no difference, i reboot it still half bright, i can however use the fn+up key to get the brightness i require but i dont really want to have to do that everytime i reboot i dont have a recovery

 

[whs]

Most laptops dimm the screen when you are running on battery only. If you right click on the desktop and go to the Catalyst control center (or whatever graphics control center you have), find the Desktop > Desktop color settings. There you can increase the brightness.