Hi,
I followed you instructions. I unplugged all of USB devices from the notebook, and then I removed the USB Hub-s (except the USB 3.0, because the problem with the USB 2.0). After I removed the USB Hubs that was the Device Manager's status: http://imageshack.us/a/img259/6194/nzt.png (The Unknown Device disappeared).
The I restared my notebook. After that the Windows 7 recignised the USB Hubs and other USB devices. Then unfortunately the 'Unknown Device' appeared again:
Recognised devices: http://imageshack.us/a/img834/386/iww.png
Device manager: http://imageshack.us/a/img855/7576/iyr.png
What should I do now?
Thank you for your help.