The first thing to do after reinstalling Windows XP, is to install your video drivers for your installed video card. This will enable you to use the full resolution and true colours.
If you have a motherboard driver, it MUST be installed immediately after Windows and BEFORE the video drivers.
Next, you may need to install your modem or network adapter drivers.
You also need to properly configure your network connectivity/internet options. This depends on your ISP and how you connect.
If you use a router between the computer and the modem, it's the router that should take care of establishing the internet connection. In that case, you only need to configure the LAN connection.
Electro, August 2011