I use NT as the develop machine. Here is the solution for NT. I think it should be similiar on Win9x machine. 
    REMEMBER: THIS WILL MODIFY REGISTRY AND SERIOUS PROBLEM MAY BE INTRODUCED. 
    1. First of all, you should check the service name of your network adaptercard. Here I assume you have one and only one network card installed on your machine. In the registry, get the value of 
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows 
    NT\CurrentVersion\NetworkCards\1\ServiceName. 
    2. Find the key of 
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\"ServiceName"\Parameters\Tcpip. Replace the "ServiceName" with whatever you get in the step 1. 
    3. Change the value of "IpAddress" to change IP address. 
    4. Change the value of "SubnetMask" to change subnet mask. 
    5. Change the value of "DefaultGateway" to change default gateway. 
    6. Don't forget to reboot your machine after you make your changes. 
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