Originally Posted by
lc_nab
Try upgrading to the latest driver for your network card, I am sure you can find them on the make of the desktop or laptop, if you built it from scratch, look for the motherboard make and download the latest NiC drivers, ( Network card )
If that does not work, try running your antivirus and maleware bytes scanner, there is a few out there that will do this to your computer.
Like Circuits said, try another network cable, if does not fix the issue, try using a usb network adapter, if it's a laptop then try the wireless instead of the network cable.
All else fails, fresh image to that pc xD or kill it with fire [ROFL1]