Wireless Adapter is a device that will receive the wireless signals and will make your computer wireless adapter. without the wireless adapter you can not use the computer to connect to the wireless network. Now a days all the laptops and desktops are equipped with the built in wireless adapters.
First check whether you have a wireless adapter on your computer ?
Right click on MY COMPUTER ==> properties ==> Device Manager ==>
you will see Network adapter ==> under network adapter you will see the wireless adapter ==> Right clink on the wireless adapter ==> properties => Check whether it says the Device is working properly or not ?If it says working properly then that's great !
WIN VISTA/ Windows 7
Click START ==> Control Panel ==> In the right hand side at the top you will see " Classic View "
Switch to classic view ==> you will see Device Manager ==> Under Network Adapters you will find your wireless adapter listed . Right clink on the wireless adapter ==> properties => Check whether it says the Device is working properly or not ? If it says working properly then that's great !
If you do not see wireless adapter in the Device manager , then either you do not have the adapter or the wireless adapter is not working .If you see "yellow exclamation mark" on the wireless adapter, that means the drivers are not installed for the adapter or not working. Reinstall the drivers.
Once your adapter is working properly , try to connect to the wireless network.
If you are installing the external wireless adapter to the computer and if you are using Windows 2000 or Windows 98 , ME, then you will have to connect to the wireless network using the utility of that adapter.
If you are using Win XP then you can use windows to connect to the wireless network or you can use other utility.
In case of Win VISTA, you will use windows to connect to the wireless network. Click Here
for more info