Wow... If I ever wondered how Dell made money, I know now...
Unfortunately, for you, Dell uses a not-so-common model of RDRAM in their 8100s. At least, so far as my research goes. And, not-so-common means not-so-cheap.
If it is what I
think it is, which is standard 64x18 PC800 RDRAM, then it will run almost right at $100 for 2x256MB from
http://www.newegg.comThe best thing to do would be to find the documentation that came with your computer and find where it talks about the memory so you can confirm that. I can't access Dells Tech Support page on the 8100 and get the info myself because you have to own a Dell computer to access that page.
Hopefully it's a model of RAM you can pick up from an OEM. If you have to buy it from Dell, it's gonna cost you
considerably more.