Yes I have verified that correct graphics driver is installed.
in Windows 8.1 It shows correct memory when running dxdiag why not in windows 7.
While in windows 7 it shows 768MB Memory while graphics card is of 2 GB.
I have contacted Dell Support but they provided one link to the driver which during installation Says Incompatible. They were unable to resolve the issue.
My Windows Experience Index says 5.7 out of 7.9 which I believe is Very low for a System with AMD Radeon Graphics.
My old Laptop without graphics had around same rating.