I've got Microsoft Security Essentials Running on Win7PE SE 32 bit with real time protection.
Files gathered from local install, the only way I could get it to work.
Virus definitions will update but will not hold after reboot but I have got a manual work around.
I'm just about ready and would like to post it in the Plugin thread as a Beta Test.
Let some one test it on Win8PE while I start working on 64 Bit plugin.
If you're interested give me a hell yea!