Right, firstly I have a Dell (get your laughing out the way) 2400 and until yesterday had only the 256 that came with it. I decided to get 512 from Scan and put it in yesterday, bit it's only reading it as 256. I pissed about in bios and thought i might be able to change it from 'single' to 'double', but it was having none of it. I've tried taking out the old ram and leaving the new one in, and it drops back to 256. It's annoying knowing that I should have 768 RAM but stuck with 512. I checked and it supposed to be able to handle two 512 sticks. Any suggestions?