Sounds like a problem with your dirvers. Go into your device manager and look for any ? marks where you should have network adapters. Start – > Control Panel – > System – > Hardware – > Device Manager. If this is the case generally you don't need anything from your ISP you need the drivers for your computer. So you need to either locate the disk that came with your computer or many computer makes such as dell and HP have their drivers on their website. You can use another computer if aviable and a thumb drive and download the drivers and then install them to your machine. This sounds like the problem since you re-installed xp.

But, it could be a numbers but I would check their first.