Convert your laptop into a wireless hotspot
Some times you just want to access the computer wireless and you dont happen to have a wifi router. 
this is what you can do 
In Windows Vista:
 Connect the laptop to the internet using the ethernet or other devices
Open the control panel and go into the Network and Sharing Center.
Set up a new connection called a wireless ad hoc network.
Give it a name and setup the desired security options.
Deselect Save this Network.
Finally, click on Turn on Internet Connection Sharing.
Now anyone can connect to your laptopââ‚ÂÃâ€ÅÃÆââ‚
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In Windows XP:

Make sure your laptop is connected to the Internet using the ethernet cable or other devices open up Network Connections. Right-click on your wireless connection and select Properties.
select Wireless Networks tab
make sure that Use Windows to configure my wireless network setting is checked
Under Preferred networks
Cick on Add button 
Enter name your network. Select shared, and provide a password. Click the Advanced button and select Computer-to-Computer (ad hoc) networks only.
Go back to the Network Connections control panel and open the Properties dialog for your wired internet connection.
Go to the Advanced menu and check the box next to Allow other network users to connect through this computerââ‚ÂÃâ€Ãââ‚Â
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