How to change the screen resolution on my Asus eee pc 1015cx

How to change the screen resolution on my Asus eee pc 1015cx

I have Asus Eee PC 1015CX and I installed Ubuntu 12.04, using bootable
USB, but unable to change the screen resolution to 1024x7687. The only
available option for resolution setting is 800x600 which looks bad on the
screen. There is no other option on the menu. How can I enable higher
resolution?
Also, checked the output (run in terminal) of xrandr -q, received the
following error:
asus@asus-1015CX:~$ xrandr -q xrandr: Failed to get size of gamma for
output default Screen 0: minimum 800 x 600, current 800 x 600, maximum 800
x 600 default connected 800x600+0+0 0mm x 0mm 800x600 61.0*
Please help to chnage the screen resolution to 1024x768.
Regards,
Satya