PC2100 Module specs

[isoflavone]

Purchased an Intel p4 1.8gb cpu and am waiting for the Intel 845-D chipset motherboards to come out. However, with the Anantech discount on Crucial DDR PC2100 memory modules i would like to purchase the memory at these low prices. Which of the following Crucial 256MB 184 Pin DIMM DDR PC2100 CL=2.5 would be the best bet for NON-SERVER use: 1) Unbuffered, Non Parity,2.5v 32meg x 64 or 2) Unbuffered, ECC,2.5v 32meg x 72 or 3)Registered, ECC,2.5v 32meg x 72 ? None of the tests of say the SIS 645 state the specs for the memory used. I read what Crucial has to say but in the back of my mind I remember something about needing ECC or maybe it was Registered memory. I know i have the cart before the horse but trying to save a buck.