If the source is external to the computer, it's possible that the connection to the external device isn't made when you reboot, especially if the external device is turned off during the reboot.

When you install the program, it (apparently) is smart enough to look for the device it needs and install the appropriate driver/codec and such - but Windows may not load the driver automatically during a reboot unless the device is turned on and connected.

When you plug in (or turn on) something new, Windows usually will recognize "compliant" devices and automatically look for the drivers, but if the external device isn't compatible with current PnP specs, it may go "unnoticed."

Just random speculation of something to keep in the back of the brain bucket while you look for real answers(?).

John