When does the message 'USB Device not Recognised' appears?
Before or after Windows start loading?
If it's in text mode as you boot the computer, you need to check your BIOS settings. Follows the onscreen prompts to enter BIOS settings and double check the properties of the USB ports.
If it's a Windows message box, you don't need to power off. ALL USB devices are hot plug/unplug safe.
Just unplug all USB devices and wait about 1 or 2 minutes. This is to allows Windows time to refresh it's USB pooling and notice that there are no devices plugged in.
Plug back the devices in a DIFFERENT port that the one they where previously connected.
Your keyborad and mice are just fine if connected to the USB 1.1 ports. Keep the USB 2 ports for high bandwidth devices, like external drives.
Electro
June 2011