|OtheHill, you are correct. We do not know if the OP has one 4 GB stick or 2 + 1 + 1 GB combination or 2 + 2 GB combination. If 2 + 1 + 1 combination and you use wrong slots on the M/B, you lose GB.|
In my M/B which has A1, A2, B1, and B2 RAM slots, if I use slot A1, A2, and B2, I lose what I install in B2 because my M/B is not able to read B2 unless B1 is populated. If I use slot A1, A2, and B1, all my RAM is readable. This is M/B limitation. I use Asus P7P55D.
I hope this gives OP some hint.