You can manually enter it in Personalization > Info. However, the CPU information you see is what the CPU manufacturer has it listed as *on the chip*. Just because it is sold as something else from some third party company doesn't change the fact that Intel's description of it is correct. As far as memory, keep in mind that Windows only sees a certain amount of memory depending on your OS, Service Pack, and certain modifications that you can do. For example, even if your motherboard supports 4GB of RAM (or more) and you have it installed, it's not going to be used by any version of XP. I'm not sure if 3GB is used by XP or not.
Again, you can manually enter the information you want displayed in Personalization, but what you see isn't really "incorrect"... it's what Windows reports.