AMD graphics problem on Inspiron 3721

Today I bought the Dell Inspiron 3721 with the following specs, according to the reseller:

Intel Core i5-3337U @ 1.80GHz

8.00 GB DDR3

1T HDD

AMD Radeon Graphics 8730M 2GB DDR3

etc.

It's running windows 7, 64bit and everything is splendid, except for the graphics.

I cannot, for the life of me, get the computer to recognize the graphics. 

I've installed all the necessary drivers for chipsets and everything else, and the graphics driver installation completes fine, but the graphics dont work - they dont show up anywhere, and the most basic of games are deadly slow.

1. In the Device Manager under displays I see AMD Radeon HD 7670M (strange since my comp supposedly comes with 8730m), with a yellow warning triangle next to it. Under properties "Windows has stopped this device because it has reported problems. (Code 43)"

(I've tried installing drivers for both the 8730 and 7670, with the same result

2. In dxdiag it only shows the default vga card, which sucks.

3. When I tried installing the Intel Graphics 4000 (comes with i5) it said my comp was not compatible or something like that. 

Please, I need you help. Thank you in advance.