USB has been a real pain. There seems no rhyme or reason.

USB memory sticks may or may not be recognised - this is on both WIN98SE and WIN XP. On some systems, they seem to keep their drive assignments, and not on others. E.g. one unit I have is ALWAYS the G drive on one (WinXP) machine, regardless of there being no F drive, even though a different unit becomes F:.

One will work on one machine, but is not recognised on another.
After installing a USB keyboard on my old WIN98 laptop, it refused to recognise my original memory stick at all, but will find the new one (Different make).

On my WIN98 desktop, it will only recognise one particular one when in a specific USB socket.

And so it goes on.