http://dl2.rapidshare.de/files/4735596/86788709/peidverarschentun.rar
maybe thats sueful for you.. disassamble em to get an idea of how its done
they are pure asm so its easy to understand
if you want to implement some known packer/crypter get some decent userdb.txt and use these EP scans to generate your own fake packer EP.
[edit]
i just got told that these exe files got packed with k_muh by messer
so seems his tool did a nice work
[/edit]