hi I have a G750JM-T4099H it has 12GB of ram installed, according to cpu-z I have 1 slot left so I purchased another 4gb ram, but when I went to install it the two slots in the serviceable area are being used. is the last slot the one I cannot access? according to cpu-z it is slot number 2. it has been back to asus for repair before where the motherboard was changed, have they just put the ram back in the wrong slot or can I not add more ram?