rundll error after nvidia uninstall

I was running XP Pro with an NVIDIA model p117. I uninstalled the drivers using Add/Remove Programs, then uninstalled the hardware in Device Manager. I shut down, swapped to a new Matrox card, rebooted, & installed my drivers.
All is well for my login, but anyone else who logs in get this message: Error loading: c:\windows\system32\NVMCTRAY.dll. The specified module cannot be found.
I searched the registry & found plenty of references to nvidia, but none to this dll.