DDR2 in DDR3 ram slot means either the DDR3 ram slot needs replacement or the mobo needs replacement.
Sorry for the confusion. the ram shd be DDR3
I'll be changing to 2 x 2Gb ram instead, it seems the mobo doesn't support a single 4Gb ram.
haha, everything is ok already.
I've shdn't have bought a single 4Gb ram as my mobo don't support it. Got it swapped with two 2Gb ram and it's working.
And Rashkae is correct, you can mix different brands ram.
Thank you everyone!