How to get better screen resolution on Ubuntu 8.04

I Installed ATI driver on Ubuntu Hardy in order to run the all wonder Compiz-Fusion and AWN.
Before the installation of the driver i was running with 1280x1024.
After the installation of the driver compiz-fusion was running wow, but my maximum resolution was 1024x768.

How can i have 1280x1024 resolution?

----- Answer:

If you are using Ubuntu 8.04 (in Ubuntu 8.10 displayconfig-gtk is no more available) try to use the displayconfig-gtk tool: please first install it, open a terminal from Applications->Accessories->Terminal and type:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install displayconfig-gtk

give your user password when requested, you don't see nothing when you type it, then press enter.

then launch it type:

sudo displayconfig-gtk

Select your monitor brand and model or try to put your monitor inf file take it from Win driver.

Then try to change your resolution from menu:
System->Preferences->Screen resolution

Hope this helps