i bought it from costco.com ,, i don't know if Dell or the seller who installed the windows , but i think it's Dell .

From Dell or a reseller?

i didn't intall the windows , it came preinstalled

Who installed Windows?  You, a shop -- or did it come from Dell preinstalled?

The Catalyst control panel will already be installed - look for it in the start screen (one of the tiles).

This model is available both with and without the AMD video chip - are you certain your system has the optional video chip?

There are two models at $800 and $900 that have it - and two models at $600 and $650 that do not, on the Costco website.

no , it's not installed , i'm sure , and i tried installing it many times , but nothing work

yes i bought the model at 800$ , and in the specification it was wrote that it has 1 gb amd radeon 7670M

I would suggest using the service tag at support.dell.com to look up the original configuration of the system - it should list the AMD video if you have it.  If you do have it, something is seriously wrong with the software installation if the drivers aren't present for switching graphics.

DVD/CD-ROM Drives

CD-ROM Drive

CD-ROM Drive

Disk Drives

WDC WD10JPVT-75A1YT0

Display Adapters

Intel(R) HD Graphics 4000 2112MB

IDE ATA/ATAPI Controllers

Intel(R) 7 Series Chipset Family SATA AHCI Controller

Keyboards

Standard PS/2 Keyboard

Mice and Other Pointing Devices

Dell Touchpad

Monitors

Generic PnP Monitor

Sound Devices

Conexant SmartAudio HD

Intel(R) Display Audio

USB Controllers

Intel(R) USB 3.0 eXtensible Host Controller - 0100 (Microsoft)

Intel(R) 7 Series/C216 Chipset Family USB Enhanced Host Controller - 1E2D

Intel(R) 7 Series/C216 Chipset Family USB Enhanced Host Controller - 1E26