I have a Dell Dimension 4550 400 MHz computer with 256MB DDR PC2700. I purchased another 256MB DDR PC2700U & 333MHz. My computer will not start up. I had to remove the new memory chip. Is there a difference in the PC2700 and the PC2700U or is it the two different MHZ? Or both?
Thanks for any help,
Your computer specs show you need DDR 333 (non-ECC) only on computers with a 533-MHz system clock speed. I couldn't find the difference in the two modules you have since you didn't post the maake/model numbers. I'm guessing the 2700U is ECC RAM (error-checking); unfortunately you cannot combine the two types of RAM - see if you can trade the 2700U for the non-ECC version from the place you got it.