I received 2-2GB sticks of DDR2-800 Crucial memory (CT25664AA800). After installing them on my motherboard next to my old RAM, I couldn't get Windows, or any CD's to boot (Windows installation disk and Ubuntu live cd). I could eventually get into the BIOS, and the system beeps reported that everything was okay, but whenever I tried to load an operating system, I either got an error or my system restarted. My motherboard is an Asus P5Q-SE2. I currently have 2-2GB sticks of DDR2-800 RAM (I forget the manufacturer), which I know has previously worked with extra sticks of RAM before. One time I added two 1GB sticks of DDR2-667 RAM with no problem. I know that the sticks are in the correct position. When the new sticks are run by themselves, there are absolutely no problems. My suspicion is that I would need to change some BIOS settings. Any help would be greatly appreciated!