The importance of names
Network filesharing problems often stem from improper workgroup and PC naming. Ensure each PC has a unique name to avoid mix-ups, don't use spaces in names and restrict yourself to 15 characters or less.
All PCs should use the same workgroup name. In XP Home the default is MSHome; in other versions of Windows, including Vista, it's Workgroup. To change either the workgroup or the computer name in XP, click Start, Control Panel, System and choose the Computer Name tab.
The Vista difference
If you're working in XP and have unresolved sharing issues, consider upgrading to Windows Vista. Its Networking and Sharing Center states which sharing features are enabled and makes configuring them easy. Vista's Link Layer Topology Discovery automatically detects network devices and shows their locations on a Network Map.
Vista's firewall is clever enough to permit sharing within a workgroup. If you're having a problem with XP's firewall, try a third-party utility. ZoneAlarm's Trusted Zone feature (zonelabs.com) allows workgroup computers to communicate.
To sidestep XP's file- and printer-sharing complexities altogether, try Network Magic. Network Magic puts all sharing and networking functions in one place. A special mode protects shared folders when your laptop is connected at a Wi-Fi hotspot, which can be a major security concern.
For more information on network security, our sister site Techworld has a comprehensive network security resource page.