Solved. Apparently the idiots at Gigabyte wrote in the manual of the motherboards "DDR1 and DDR2" Which confused me. Apparently both slots are DDR. and the DDR1 and DDR2 are to refer to DDR Slot #1 and DDR Slot #2. It was all misunderstanding. Hence it explains my DDR RAM can enter easily with no problem at all in both slots. Thanks all!