I recently built a computer for myself and one for my brother. They are almost identical computers both running XP. I started out with 2GB each. I recently decided to purchase another GB for each computer. So I bought (2) 2X 512MB so I could keep the Dual Configuration. I installed them both into my computer and my brothers. Then I checked the basic info on each computer. My brothers says it has 3GB as it should, however mine only says it has 2.5GB. Do I have a faulty RAM? or is there a setting that I have to change. I am very new to building computers, so any help would be appreciated. Oh and all the memory is Corsair.