A classic problem with XP file sharing

Q: Our department has two computers with Windows XP installed, all open the Guest account, but now there is such a problem: Machine A can access Machine B normally, and Machine B is accessing the machine. A, the prompt does not have permission and can not be accessed, please contact the administrator of this machine. How can I solve this problem?
A: Machine A can access machine B, indicating that there is no problem with the physical connection between the two computers. The main reason may be the system setting in machine B:

Reason one: The firewall in the system of machine B prohibits the access of the A machine. You can change the settings related to the firewall. For example, if the firewall that comes with the system is turned on in the B machine, the A machine must not be accessible.

two reasons: the system registry machine B is set in a ban being accessed, open the Registry Editor, view the key "HKEY_LOCAL_MacHINE \\ System \\ CurrentControlSet \\ Control \\ Lsa" dWord type of key items "restrictanonymous The value of " is not 1, if it is 1, changed to 0, it can be accessed after restarting.