i'm not sure why DELL website also show 2 options there?
maybe let customer to choose?

after i searched AMD website spec, AMD Radeon HD 7670M is delivered HD only.

so the seller give wrong info to buyer.

my mind is,

1.maybe the laptop display is only support HD, but if you connect to Full HD TV/monitor via HDMI, it will show up Full HD?
Have you try this before?

2. try to update the display driver from dell. There are update there.
25/10/2012
http://www.dell.com/support/drivers/my/en/...driverId=3W32N#

14/6/2012
http://www.dell.com/support/drivers/my/en/...leid=2988273566

3. Or you need to install " AMD Catalyst Mobility drivers" to get the FHD?
http://support.amd.com/us/gpudownload/Pages/index.aspx