I figured I’d quick throw this out there, as I’ve spent some time trying to figure this issue out. In my experience with Windows Deployment Services (WDS), I found out that when I was trying to boot up a x64 system, sometimes it will only use the x86 boot images. It turns out that you need to manually turn on the x64 discovery mode on the WDS server so it can properly detect if the system you’re booting up is x86 or x64.
Open the command prompt, and enter the following:
WDSUTIL /Set-Server /ArchitectureDiscovery:Yes