Two sets of orange + yellow slots. Why is it that my RAM is only in the orange slots? Can I buy the exact same 2x2GB RAM and stick both of them in the yellow slots to double my RAM? Sorry for the question, don't laugh too much.
Unfortunately adding RAM, even of the identical model, does not always function without issues. It's always best to buy ONE, tested, matched RAM kit of the quantity you desire. Some folks do add RAM and it works, but many folks have learned the hard way this is not always true.