usb device not recognized in windows 7

usb device not recognized in windows 7

When the USB device such as a USB keyboard is connect with my computer, I get a fllowing error message:

USB Device Not Recognized
One of the USB devices attached to this computer has malfunctioned, and Windows does not recognize it.
For assistance in soling this prolem, click this message.

But I find that my computer's USB ports works fine. I installed windows 7 and they were working fine.
Then I uninstall the drivers for my devices and reinstall them. The USB doesn't work. I open the Device Manager Window and see all of the devices under USB Controllers there. Uninstall them and restart the computer. After reinstall the USB drivers, the problem is still.

How to fix USB device not recognized in Windows 7 system? It's simply to solve it. You just unplug your computer from the power supply.