Hi, I am using ubuntu 8.10 on SONY VAIO labtop(model no. VGN-CS12GH/B).
The problem is that the brightness of screen does not change. I tried the shortcut given on the keyboard for brightness control (with Fn key), and I also tried the brightness applet located in panel but still ubable to change the brightness of the screen.
The machine having the Graphics of Intel named as: Graphics Media Accelerator 4500MHD

Please help me..

Perhaps you should use the function key and try different F keys, maybe the brightness control keys on your keyboard (say F7 &F8) aren't the same in the generic keyboard driver under Ubuntu, so you could try the function key and different 'F' keys and see if any others will adjust the brightness. That's the only thing I can think of right now, although I will try some searching to see what the "generic layout" is according to linux. Worth a shot and I will reply if I find out what the layout is. Hope this helps or you have already gotten it taken care of..

Edit: Actually, I looked it up and according to wikipedia (take it for what it is) Function F2 should do the trick. Or not, but it's worth a shot.

Thanks for your suggestion.
But still the problem persists.
I tried Fun. Key with different F key but the brightness does not change.

Wow, I really thought we may have caught it with that last suggestion, but we will not give up, let me do some more research and will post again (hopefully tonight) if I come up with anything that I think may be worthwhile. Sorry this one didn't work, but if at first you don't succeed, try again, and then drop kick the keyboard, right?