Hi and welcome to TechZonez

that is a nice big jump in specs, skipped win2k server. SBS2k3 is great, we are resellers and its an excellent package with everything they need First off what role does your NT4 play and what is it used for and whats installed etc

As it is quite old, I would almost be tempted to just bring the NT4 server down, and install SBS2k3 in and configure. Dont worry about the 266, try to sell it

Let us know how you go.