The USB stopped working at a Dell 1545 laptop with Windows 7 x86 Enterprise.

Symptoms:
– All the USB devices plugged were -> Unknown device

Solution:

1. Go to Control Panel, select Small Icons from the upper-right menu (View By), then go to Device Manager:


2. After the new window appears, click Universal Serial Bus controllers to expand. After that click on each item selected below and press DEL.

3. And now click OK, after that go back to step 2 and select the next USB Root HUB and press Delagain, until all are deleted, then go to next step.

4. Unplug all USB devices, power off the machine, leave it off for a few minutes ( if you have an laptop unplug the battery ), then power it back on.. and enjoy the USB device again.

ENJOY.

And if you encounter any problems feel free to comment / contact me.