I'm typing this reply using a home-built P4 2.4Ghz D845PEBT2 Intel system very similar to your Dell box. It also has 2 dimm slots. My Intel board accepts 1GB sticks of ram. Your Dell does not. They were made at roughly the same time, so technology is not the answer. If you go over the limit the only thing bad to happen is that the system may not POST, making it useless until you go back to 512MB per dimm.