FPPWS as it is often called is the smallest (and crapiest) of the personal web servers that Microsoft supplies. It only ships with Frontpage 97, 98, or 2000 (and there is a special trick to installing it from the Fp2k cd. It has no security - meaning you can't give anyone else author permissions, and it is very easy to break into or crash. You should never use this pws unless somone is threatening to kill you (and even then it's a tough decision).