Many Wireless cards' drivers also install the vendor's Wireless utility.
Make sure that if there is a vendor's Wireless Utility is Not Running together with the Windows native Wireless utility (WLAN Service) .
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Forcing Win 7 to install the most updated, Drivers sometimes help too.
When trying to update the drivers by just pressing on the Update feature in the devices’ entry in the Device Manger the computer checks the drivers on Microsoft Update server.
However, the Drivers on the Update server are not always the most updated drivers. The manufacturer might have newer drivers that were not yet submitted to the Update server.
Try to install the latest drivers of the card from the support page of the manufacturer.
Download the drivers and unpack them to a folder of your choice.
In the Device manger, right click on the adapter.
Click on Update Drivers, and choose the Browse my computer for drivers,
Choose let me pick from a list , Click on Have a Disk and point to the folder with the Drivers.
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In general we tend to ignore, the fact that Wireless largely depends on Signal Propagation.
If an Antenna in a Laptop is Not designed optimally for Wireless receiving/transmitting. If there is some loose contact in the connection between the Wireless card and the Antenna, or the Laptop tend to get hot and it reduces the Wireless card power output, it does not matter what you do you will Not get good Wireless.
Sometime it is better to get a spare good Wireless USB dongle, and use it in cases of mission critical.
As for Wireless Signal strength read this,
http://www.ezlan.net/wbars.html
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In many laptops the Wireless card is set to reduce power in order to save on battery.
First boot to the BIOS and check the Wireless card features (if any).
Then Uncheck the Network Card's Power Saving (I.e., do not let the card save power).
There might be some variations on where the Power saving setting is.
Here are few examples, YMMV, look around in your systems.
Example,
http://www.ezlan.net/example/powersave.jpg
Example,
http://www.ezlan.net/Win7/power_sav_wireless..jpg
Example,
http://www.ezlan.net/Win7/power_save_win7.jpg
Example,
http://www.ezlan.net/Win7/adv_power-sav.jpg