So there was a topic on the General Help and Support board where the poster mentioned it was not easy to check if the system was installed with UEFI or legacy mode and it got me looking down a rabbit hole. Apparently you can't just whip up a simple WMI query to find that out. But I did find that you can read the output of bcdedit.exe to check if the system is using winload.efi or winload.exe, so then I got stuck because bcdedit doesn't play nice with StdoutRead. Finally I discovered that to