Bleh, this is getting more convoluted all the time.
I was unable to logon as that user until "log on as a service" was set. JoyToKey would run, then, but still wasn't doing anything.
Left the logon and password blank so that I could turn on "interact with the desktop", and that seemed to work.
From the FireDaemon documentation "If this is left blank the service will run as the LocalSystem user. Services running as any other user except LocalSystem cannot interact with the desktop. This is a Windows limitation."
Also added a nice long delay (10 sec) before JoyToKey boots.
If I pop open notepad, I can 'type' with the gamepads (yay), but once JoyToKey loads this way, I start getting directinput errors from the emulators.
The frontend (shell) will load, and I can quickly open an emulator before FireDaemon starts JoyToKey, and it'll open fine. Escape out of that back to Mamewah. when opening the emulators. I'm so lost
Update You can set XP to run a script (.bat etc.) at startup or login by running gpedit.msc and navigating to User Configuration > Windows Settings > Scripts > Logon or Computer Configuration > Windows Settings > Scripts > Startup
I've got a .bat that just has
@echo off
start /min <Path to JoyToKey>
and that seems to be doing the trick.