Hi, I'm assuming you are talking about RD Ram, which will need to be installed in matching sticks of 128 to total 256.
I was able to up my Dell 8200 to 512mb and save $50.00 at "Upgrade Nation" on the same Ram as Dell sold.
One important factor will be the NS #, which will be either 800-40 or 800-45. Take a look at your existing sticks and be sure to order the right NS, as they are not compatible.
I have a Dell deminsion 8200, and I am looking for a good price for 256 mb ram. I know I need 184 Pin, pc800, ECC. At the Dell site they state that the logical type is 128 x 18, but I've only found 128 x 16 (yet meeting all other specs) at other sites. What is "logical type" and how important is it?