Dual graphics

Need more info. What is the model and manufacturer of the computer? Complete specs would be helpful. What CPU does it have. That sounds like you have an AMD APU with built in graphics plus a discrete Radeon HD 7670M graphics add-on card. Is that correct? Which APU specifically?

AMD A8-4500 with Radeon HD Graphics (4 cpu's), ~1,9ghz
4GB RAM
AMD Radeon 7640G + 7670M Dual Graphics

yes 2 GPU's are better. They dont double the performance but you will notice better power.

You can download GPU-z (linked below). it should say crossfire enabled or disabled.

sometimes you have 1 onboard and 1 discrete card.

what make/model laptop are you running?

http://www.techpowerup.com/gpuz/

ASUS A75D series

It's not two graphics cards. The 7640g is the Integrated Graphics Processor (IGP) of a Amd Trinity chip, in your case the A8-4500m. The 7670m is a dedicated card with GDDR3 memory. In theory they can run in hybrid crossfire (dual graphics) and you will get a speed boost. To put it more plainly, notebookcheck has the 7660g+7670m (A10-4600m processor and dedicated 7670m) rated at only 1% below a GT 650m, however, that's if the application (game usually) supports the dual graphics. Currently there are not enough titles that properly support it so you usually have to make a profile under catalyst to specify the use of the 7670m. Over the next year though, as drivers mature for trinity dual graphics, and more games begin to take advantage of it, then it should become a hot topic for low budget gamers.