I am currently running XP, and I have dual channel memory. Right now I have x2 1GB DDR2 RAM chips (so 2GB of RAM) They are in the corresponding slots. I'm thinking of getting more RAM, but because XP can only see up to below 4GB of RAM, would it be better to get 2 more 1GB chips? Or just one 2GB chip? (I can get 2GB cheaper) If I was to have the two existing chips running on dual memory, am I still able to just put in one more chip of ram, while leaving its other corresponding slot free? Thanks a lot.