Have you tried,
Start/ Settings / Control Panel / System / Device Manager / Refresh ?
Go through that "refresh" and let the system find all the 'bits' again. Once your mouse 'arrow' can move again is the time to try that scanner.
If you have Win 98 the system should recognise there's a scanner there no matter when you switch on - but Win 95 is not that clever, and needs the scanner on FIRST then the PC to be switched on.
So if you have W95, keep the scanner on, go to Start and select, "restart" and let the thing fire up again - see if that helps.