Do you mean that you already have a 128 mb stick in there? (1280mb is what you listed) Remember all RAM is not compatible with each other. If you do indeed have a 128 mb stick in there, get rid of it and get you two 512 sticks. This is much cheaper. What motherboard are you using and what OS? I'm sure it's Win XP or better. If it happens to be Win 98 save your money as 512 is the limit. Since you are using DDR 400, I'm going to assume your system is pretty new. I just don't see why it would have only 128mb of RAM. Now my final question is: What are you running that needs more than a GIG of RAM?
3 different OS, so yep I\'m confused.