start explorer, select Tools - Folder Options, click on the view tab, scroll down and check "use simple file sharing (recommended), then press OK. If that doesn't solve it go to the control panel, select network connections, and run the network setup wizard and make sure you select the correct workground name (normally you do that when you install XP but so far every time I reinstalled I still had to run this wizard, after that an rebooting things worked just fine).