I took my system to the shop to have it tested and there wasn't any screen flickering with their monitor. Hence, they didn't replace it. But, when I came back to my place, I still see a bit of flickering in COD4 MP game but no more during boot up.
My monitor(View sonic 17 Inch LCD) works fine with my old gpu(Nvidia GT 220) but not with this new GPU.
I'm just having all issues since I purchased this new GPU. Really dishearted.