While installing the cpu fan (intel stock), the 2 right handed "legs" clicked into the motherboard (Gigabyte GA-P35C-DS3R) with the white plastic on the other side and a black prong in the middle. However on the 2 left sides, the white part went threw, but not the 2 black prongs...I tried pushing with reasonable force to get the black prongs in, and nothing happened...what do I do?