We have a D-link DIR-655 router in the garage, fed by a DSL modem and routed around through CAT-5 cables to various rooms in the house. About two months ago, we upgraded my son's computer (new motherboard, processor, memory, video card, sound card, power supply - old drives and case) and installed Windows 7 on it. Looking back, it was at this time that my wife's Vista Home laptop started losing its wireless connection.
We tolerated this for a while, and then decided to replace the DIR-655, reasoning that it could have developed wireless problems after two years of great service. When the replacement arrived, we hooked it up, got everything working just right on the wired side of the network (two computers, one of which has two printers plugged into USB ports to serve out over the network), and then turned on a laptop to confirm that the wireless was fixed.
It was, for a few minutes, and then, the signal disappeared. So, we called D-link tech support and administered a whole bunch of possible fixes, none of which worked. We were told to pack it up and send it back, so we did, and a couple days ago, the second replacement arrived.
Last night, I finally got time to hook it up, and it acted exactly the same. The wireless stayed up for about a minute, then suddenly disappeared.
So, the kid, whose date memory is better than mine (that's what 50 years of age difference will do for you;-)) says, "Y'know, Dad, this problem started about the time we upgraded my computer - let me go try something totally weird." He shut down his computer, and, lo and behold, the wireless signal came right back on, and stayed steady while we watched on online TV episode for the next half-hour.
We have the Dell wireless utility on the laptops, and can see the signal-to-noise ratio graphically. With my son's computer turned off or disconnected from the network, we see no discernable noise, and -50 db of signal (which corresponds to four bars on the icon). As soon as his computer comes online, the noise bars jump up to the same height as the signal bars, and, after a matter of seconds, the wireless part of the DIR-655 shuts down.
There is no effect on the wired part of the router - not so much as a hiccup.
We thought maybe the kid's computer had a wireless adapter in it that was doing this, but we checked, and there isn't one in the box. To see if his computer might be radiating some signal, we unplugged his network cable. The wireless came right back on and stayed on until we plugged him back in.
He's using the on-board network adapter to hook up. I have a bunch of older PCI network cards, but Windows 7 won't recognize any of them. Our next ploy is to find a compatible PCI net card, disable the on-board adapter, plug the card in and see what happens.