My mb handles the 4 GB. Windows XP is the limiting factor. However my computer runs sweet with the 4 GB. I score about 16,500 on the 3D Benchmark test. I run every game maxed and have no slow down. I agree that the 4 GB was over kill. If I could do it again I would get only 2 GB. However at the time I was designing the computer on this web site nobody informed that 4 GB was a problem.