I have an Airis desktop PC with a Gigabyte GA-8VT880P-COMBO-(REV1-X)motherboard with an Intel P4 Dual-Core.. It has 2x 512MB memory sticks fitted. I want to fit 2x 1GB DDR2 PC2400 533MHz sticks, so I will have a total of 2GB of RAM. Do I have to remove the previous 512MB sticks? Is there any benefit to leaving them in?