changing the screen resolution of the external monitor using IBM thinkpad X61s and ub
 

Hello

I am new to linux and got stuck on my first day.
I have IBM Thinkpad X61s. I installed "Ubuntu 8.04 - the Hardy Heron" on it. now i am trying to connect samsung LCD monitor to the system. when i press FnF7 then my external monitor is cloned and I see the same screen on both laptop monitor and on LCD. then i tried to change the resolution of the monitor with the "screen resolution" program but it has no effect. it says that the external computer is cloned. if i disable the clone even then i cannot increase the resolution. the maximum resolution i am getting is 1024x768 (both on laptop and external monitor). i dont know how can i increase the resolution when connecting to the external monitor.

does anybody has any solution for this problem.