I agree with Kisianik, I actually have a 745 (mid tower) that I use as a home theater pc, and couldnt get it to recognize more than 4GB of RAM unless I used 4 matchings sticks. Also be aware that as soon as you hit 4GB+ in the 745, the bios knocks the speed down to 667Mhz, even if you are using 800Mhz RAM. Not sure why, but maybe a chipset limitation or just Dell being stupid (like normal).