With wireless, you can get interference from neighboring wireless routers that use the same channel - you may have to manually change the channel - or some routers are clever enough to get a signal with least noise.

The most useful thing (and about the only facility that I will regret losing when I move from Win 7 to Linux) is a cute radar like display called ConfigFree from Toshiba that displays all net connections available - the Lan link if plugged in, and all wireless links around - their name and mac address and IP address if hard wired.

If you can find a utility that works like this for basic Windows, you will instantly see if any other wireless links may be nearby and possibly interfering.