i can't change my graphics resolution,i'm using 11.10 on a dell mini inspiron

Can you give the output of:

sudo lshw -C display; lsb_release -a; uname -a

Thanks

root@john-Inspiron-1010:/home/john# sudo lshw -C display;lsb_release -a; uname -a
  *-display
       description: VGA compatible controller
       product: System Controller Hub (SCH Poulsbo) Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 07
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi vga_controller bus_master cap_list rom
       configuration: driver=poulsbo latency=0
       resources: irq:7 memory:d8100000-d817ffff ioport:1800(size=8) memory:d0000000-d7ffffff memory:d8380000-d839ffff
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 11.10
Release: 11.10
Codename: oneiric
Linux john-Inspiron-1010 3.0.0-14-generic #23-Ubuntu SMP Mon Nov 21 20:34:47 UTC 2011 i686 i686 i386 GNU/Linux
root@john-Inspiron-1010:/home/john#

This means that you don't have any driver installed. Have you checked if there are any Additional Drivers to be installed?

i,ve checked all that. no drivers to install.
i did have this pro with natty but did something in terminal to sort it out.i just can,t remember the input commands i was given.

Ok. Please follow these steps:

1.- Search the values of HorizSync and VertRefresh of your monitor.
2.- Open a terminal and type "sudo X configure :1" without quotes. This will create a new xorg.conf file.
3.- In the same terminal, type "gksu gedit xorg.conf.new" without quotes. This will open a text editor with the file that you have just created in there.
4.- You will see that it is divided in sections. Search for the Monitor section, and before the EndSection line of that section, add this two lines, without quotes:
"HorizSync 30.0 - 81.0
VertRefresh 56.0 - 75.0"

5.- Replace the values in there with the values found in step 1.
6.- Save and close the file. If you want to, you can put it into a pastebin so I can check it before you move. If you do not want to, then move on to the next step.
7.- In a terminal, type "sudo mv xorg.conf.new /etc/X11/xorg.conf" without quotes. This will move the file to its correct position.
8.- Restart the PC.

In case it does NOT works, copy this command into a paper: "sudo rm /etc/X11/xorg.conf", and boot into text mode, to enter this command without quotes and remove the file. If it works, please ignore this step.

Haveing the same issue. How do I check for drivers? My command output shows descriprtion: UNKNOWN

José Antonio Rey suggests this article as an answer to your question:
FAQ #1901: “Intel Chipsets Screen Resolution Problem”.