First try unplugging (and removing the battery on a laptop), press the power button for five seconds. Leave it for two minutes and try the USB again.
If that doesn't work...
Restart in Safe Mode*
Open Device Manager, click Start, and then click Control Panel. Double-click System. On the Hardware tab, click Device Manager.
Double click Universal Serial Bus Controllers/USB Root Hub (X Ports). Right click each instance underneath and uninstall the drivers. Don't worry, Windows will re-build them.
Restart normally and try again.
*Note: On start up (before Windows loads) keep tapping either F5 or F8 (be aware that some manufacturers use F8 for system recovery!) then use arrow keys to highlight 'Safe Mode with networking' and hit Enter/Return, click on a user account, enter the Administrator password (if you don't know it, there probably isn't one so leave it blank) and hit Enter/Return.
Try this for your CD/DVD drive...
Turn off PC/laptop.
Disconnect CD/DVD drive*, turn PC/laptop on, allow to boot fully, then turn off again.
Re-connect CD/DVD drive and turn on.
Windows will re-build the drivers or start the 'Found new hardware wizard'.
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