resolution poor

Hi there.... did some of you know how to fix this little problem? Whenever I boot to MacOS, the Apple boot logo seems to be stretched, after it loads for about half, then it started to look normal (native resolution) and After half the loading screen : I have tried CsmVideoDxe, but...

So I have a: Intel Core i5-3570K Ivy Bridge 3.4GHz (3.8GHz Turbo) LGA 1155 GIGABYTE GA-Z77X-UD5H SAMSUNG 840 Series MZ-7TD250BW 2.5" 250GB SATA III Internal Solid State Drive (SSD) And 8gigs of Corsair RAM When I turn my computer on, the resolution is terrible, and the only option it gives me...