i have a dell dimension 2400 and i am trying to upgrade it. it only has 256mb worth of ram in it so its pretty slow. i bought a 400mHz 1GB ram and i wanted to use this with the original ram. when i put it in the computer though, it wont start up. i'll turn on the pc and at the very begining, when the BIOS is loading i think, the loading bar just stops. i dont know what to do. please help.