How to extract Windows PE from Longhorn
Windows PE in longhorn is actually fun to toy around with. Ive used it to build an emergency recovery CD. Its the core of windows (mouse drivers work in every build EXCEPT 4074. only use windows PE from 4029 and above) made to boot off of a CD. Using the instructions provided in the link, you can make it so that the command prompt will load on startup
Its not a replacement for BartPE, but you can make some fun stuff out of it.
I will not help you find any builds of longhorn to use for the extraction process.