We have a svf142c29m touch screen laptop with 8Gb RAM, 1.80Ghz i5-3337U CPU, 270Gb Hard disk. The laptop is making a strange low noise when we unplug the network cable. a bit like a fog horn in tone and pattern. Its still as from factory. Nothing is coming up in the system logs. There is no antivirus, but we have tried it with Mcafee (came with laptop), Avast Free and AVG Free as well making the noise with all 3. The operating system is Windows 8.