I have a 1.6GHZ sempron (AMD) processor on a MSI k8mm-ILSR board. The FSB of the board is 200mhz with a BIOs feature that will set it up to 280mhz. The Bios also allows a selection for DDR400 memory that should run on this system even though the FSB is only 200mhz. Recently I put a 1.Gig stick of DDR in the vacant slot next to the 256meg of DDR400 that was already there. System info only recognized the 256. I took the 256 out and left the 1gig. System started and system info reported 512meg for the 1gig stick. I exchanged the 1gig stick for (2) 512meg sticks, put them in and system info reported only 512meg. Taskmanager reports the same as system info in every case above. My operating system is MS W2k advanced server with service pak 4.1. I have SQL server on the box also. The new (2) 512meg sticks are a different chipset than the 1gig. If anyone can help...I am listening closely, Thanks.