Your school may be the problem here. Many schools nowadays block or shape p2p programs because they use too much bandwidth which schools pay a lot of money for.

Make sure XP's firewall is disabled. And configure Norton firewall: Configuring Norton Internet Security.

If still no go, try changing ports to one between 49152 - 65535. ie: go to FrostWire's menu bar, Tools>Options>Advanced>Firewalls & change port numbers. Then restart FW.