If you have a laptop with a wireless network card, and want to log on to a different networks (i.e. company network and home network) without having to manually change the TCP/IP settings each time. Assuming your Operating System is Microsoft Windows XP and that the office network uses DHCP but the home network is assigned a static IP address - Microsoft provides great feature to XP and Server 2003, called Alternate TCP/IP Configuration. To use it, do the following:

1. Go to Start | Control Panel | Network Connections.
2. Right click the icon for your wireless connection and select Properties.
3. On the General tab, scroll down and double click Internet Protocol (TCP/IP).
4. On the General tab, select Obtain an IP address automatically (this configures the computer for the network that uses DHCP).
5. Click the Alternate Configuration tab (this tab does not appear if you don't have the General tab configured as described in step 4).
6. Select the User configured option, then type in the TCP/IP information for the network that uses a static address (IP address, subnet mask, default gateway and preferred DNS and WINS servers).
7. Click OK twice to close the dialog boxes.

Now when the computer can't find a DHCP server (that is, when you're connected to the home network), it will use the alternate configuration information you entered.

Please note: this feature is most useful for those of you that have manually assigned IP addresses to the computers on your home or business network. If you are using Internet connection sharing devices that automatically assign an IP address, default gateway and DNS server to your computer, you do not need to fill out the entries on the Alternate Configuration tab. Your computer will use the settings on the General tab to automatically obtain IP addressing information from your Internet connection sharing device.