I am absolutely stumped.
We have cable Internet service shared throughout our home by a Netgear 150 Mbps wireless N router. All but one of our computers typically perform well, and tests run at speedtest.net consistently show speeds of around 10-11 Mbps.
We have one desktop computer, however, that routinely tests at less than 1 Mbps -- often down around 0.5 Mbps! -- and always handles the Internet at a snail's pace. I have done everything I can think of. I've replaced both the wireless adapter on the PC and our wireless router with new units in case they were malfunctioning. I've wiped the PC and re-loaded Windows 7 (Pro x64) from scratch. Nothing changes.
I've brought other computers into the same area of the house to make sure something wasn't killing the wireless signal. Nope, they do fine.
Any idea what could possibly be causing this?