The boot screens are actually modified Windows Kernels (the very basic form of an operating system) unless you want to use an older and possibly incompatible kernel I would suggest against it.
Well I found my answer, and I was correct, those files are used for upgrading the original Media Center to the 2004 version. Upgrading to Windows XP Media Center Edition 2004
What are the Media Center files for in service pack 2 (if you extract the network install) are those files used to update Windows XP Media Center Edition to the 2004 version?