Repair the connection—
Windows 7’s network repair tool seems to work particularly well for
solving wireless woes, so you should always start with that.
Reboot and power cycle devices—
Reset your hardware by performing the following tasks, in order: Log
off Windows 7, restart your computer, power cycle your computer, power
cycle the wireless access point, and then power cycle the broadband
modem.
Check connections— Make sure your wireless NIC is installed properly and that the antenna is attached securely.
Move the antenna— If the wireless NIC antenna is on a cable, move the antenna to a higher position.
Check your notebook WLAN switch—
Many notebook computers come with a switch or program that turns the
internal wireless NIC on and off. Make sure you haven’t inadvertently
turned the NIC off.
Look for interference—
Devices such as baby monitors and cordless phones that use the 2.4GHz
radio frequency (RF) band can play havoc with wireless signals. Try
either moving or turning off such devices if they’re near your wireless
NIC or wireless access point.
Caution
You should also keep your wireless NIC and access point well away from a microwave oven; microwaves can jam wireless signals.
Change the channel—
You can configure your wireless access to broadcast signals on a
specific channel. Sometimes one channel gives a stronger signal than
another, so try changing the channel. You do this by logging on to the
access point’s configuration pages and looking for a setting that
determines the broadcast channel.
Check your range—
If you’re getting no signal or a weak signal, it could be that your
wireless NIC is too far away from the access point. You usually can’t
get much farther than about 115 feet away from an access point before
the signal begins to degrade (230 feet if you’re using 802.11n devices).
Either move closer to the access point or turn on the access point’s
range booster feature, if it has one. You could also install a wireless
range extender.
Check 802.11b/g/n compatibility—
For your wireless NIC to work properly with your wireless access point,
both must use a compatible version of the wireless 802.11 standard. For
example, if your NIC supports only 802.11n, but your access point
supports only 802.11g, the two will not be able to connect.
Reset the router—
As a last resort, reset the router to its default factory settings.
(Refer to the device documentation to learn how to do this.) Note that
if you do this you’ll need to set up your network from scratch.