Arduino UNO Rev 3 not recognized (code 43)

I have this problem for some months now and I don't know what to do. When I plug my Arduino UNO Rev 3 into my pc (win 7) it says 'usb device not recognized' and the device status says 'code 43'. I tried everything: differen pc, new usb cable, update driver. The arduino environment doesn't recognize anything. Please somebody help me! Thanks