Your voltages are ok but the Ping test shows the internet connection is not so good, this most likely because of the way that your hardware is connected up, if you are able to, one way of testing this would be to set up your computer closer to the first router or at a friend or family members home to see if there is any improvement, ideally plugging in a wireless dongle and connecting to a wireless router as that would show what your other hardware is capable off.
As an asides, a router Firewall was another thing that I suspected but you have said no one else has an issue making the distance from the computer to the router more likely
Edit to add;
See how your video card performs by running the Valley benchmark (free) here, one way of ruling out another possible cause if nothing else.