In message ,
brugnospamsia writes

typical windows-type problem - had same trouble a few weeks ago with a
colleague's laptop (W98) that had decided to stop recognising his USB CD
drive - uninstalled and reinstalled everything. Drive worked straight away
on another (Win2K) machine. The USB printers on my office machine (Win2K)
periodically "vanish" - though haven't had to do anything more drastic than
re-boot ...

Try disabling "Allow the computer to turn off this device to save power"
in the relevant USB root hub properties.