It might be because your computer has lost its IP address, this happenned to me and happens every now and then. It probably happens because of my Linksys router because I never had the problem before I had a network. You don't have to do a fresh install of XP to fix the problem, I've found that a System Restore to a date when the internet was working fixes the problem. As for your network, reconfiguring the network is the only way to get it working again.