Hi Steve,
Here are a couple of things to try:
1 Turn off the computer and remove the plug from the wall socket (also remove the battery), leave it for half an hour and then plug back in and re-boot.
2 Enter the BIOS at startup (tap F2) and restore the default settings.
3 Uninstall all USB controllers in Device Manager and then re-boot.
If none of the above have any effect then you may possibly have a hardware fault. No doubt other members will offer further solutions....
Go n-éirí an bóthar leat
