I have been researching this topic a lot and I still keep having this issue where my WinPE.iso will not boot. I have it (and the memdisk) stored in an easy access location, all have proper ownership and permissions, but still states that there is no file or directory when I try to boot it.
(ex. menu)
:WinPE
initrd http://10.101.xx.x/ISO/WinPE.iso
chain memdisk iso raw

I have tried to use the ipxe/winpe help website that is often included in the forums, but it still has not helped me resolve my issue. Can anyone lead me in the right direction to get this to work? Thanks.