But then the screen flickers. The system reboots automatically—that’s the hacked boot.ini’s “failover” mode. The second attempt works. The USB remaps itself as C:\ . The traffic light software launches automatically from startup.

First attempt: imagex.exe /apply. I pour the XP install.wim onto the USB. Plug it into the test rig—an old HP Compaq. The BIOS sees the USB. It begins to boot. Then: .

I run devmgmt.msc . No yellow bangs. USB root hub is happy. The traffic light simulation software loads. It talks to a serial-to-USB adapter connected to an Arduino blinking LEDs in my kitchen.

I try again. And again. I try every USB mass storage driver from the XP driver cab. I hack the registry—adding Start=0 to usbstor , usbhub , usbehci . Nothing.

He hands me a check. It clears.