Here is a list of things to check when your having problems sharing files on Windows XP

Check the Network Connection/Adapter:

- Go to start, control panel, open network connection, right click on network adapter and click properties, make sure theres a check in file and printer sharing checkbox. If not, put a check in it and click OK to save that setting.

Reset the Windows Firewall:

- Go to start, control panel, open the Windows firewall, choose advanced tab, click reset defaults

- then make sure you go under exceptions and put a check in "file sharing" to allow file sharing

Check Local Security Policy: (Access this computer from the network)

- For maximum security:     Administrators, Authenticated Users, Everyone

- Defaults:     Administrators, Backup Operators, Power Users, Users, Everyone

Check Local Security Policy: (Network access: Sharing and security model for local accounts)

- set it to "Classic: Local users authenticate as themselves"

Setup File and Printer Sharing:

- Go to start, control panel, network connections, network setup wizard, choose either "this computer connects directly to the internet" or  "this computer connects to the internet through a residental gateway". The first one says you connect directly to a modem. The second one says that you connect to a server or router which connects you and others to the internet at the same time.

- Then give your computer a name and click next, then choose a name for your workgroup of enter the same workgroup everyone else is using on your network then click next, then choose "just finish network setup"and click finish. You will then need to reboot your computer.

NOTE: Firewalls can also block file sharing, if your still having trouble try uninstalling custom firewalls and disabling the windows firewall.