It's safe, go ahead, you already installed it so nice for you
. I was referring to 6670 1GB Because it's faster. But since you already have it you are OK staying with it.
Well what do you mean by can't go by 1920x1080? The resolution stuck/maxed out on lower resolution? Maybe your friend got confused of normal/regular HD which is 1280x720 (mostly they are not like this instead they are 1366x768 monitors) and full HD which is 1920x1080. And your friend's native resolution of his/her monitor maybe is not 1920x1080, please confirm that and if you don't know just provide us the model number of your monitor. However if you are sure that it should reach 1920x1080, you may try updating drivers (both monitor and graphics). Come back and good luck