I own an hp h8-1080t which has 12g of factory ram. I believe it is 2x/2g and 2x/4g simms. Am interested sometime in the future to add another 12g making 24 total. Here are my 2 questions. 1) do I need to lose the 12g that's installed or can I just add the other 12 matching speed and type. 2) I have seen on several Mb including this one, Blue slots. What is the significance.