I would start by:
- Checking the PXELINUX.cfg\default file on the PXE Rep.
- Checking the SYSLINUX website (which I just went to and it says it is currently out of order but you can check a mirror) for the latest versions of the SYSLINUX files.
But this isn't a Linux, it's WinPe Image
Sure it has the word "LINUX" in it, but SYSLINUX is not Linux.
SYSLINUX is a network boot technology that supports password protected PXE, and it is the technology we use for our password protected PXE.