When you type an Internet address into the browser, Windows XP uses the local route table as a network map to determine where to send the packet. In most cases, the route table directs the packet to the gateway, which then sends it out to the Internet.
However, you can configure the route table to send packets addressed to a certain Web site to a dead end. The result makes it appear as if the site doesn't exist.
To begin, you need the IP address of the Web site to which you want to block access. You also need an unassigned IP address within your local subnet that isn't in use by any computer or device.
For example, let's say that the IP address you want to block is 100.100.100.100, and an IP address on your local subnet that isn't in use is 192.168.100.51. Modify the route table with the following command:
Route -p add 100.100.100.100 mask 255.255.255.255 192.168.100.51
For more information on the Route command, check out the Windows XP Help and Support Center.