LM authentication is not as strong as Windows NT authentication so you may want to disable its use, because an attacker eavesdropping on network traffic will attack the weaker protocol. A successful attack can compromise the user’s password. How do you disable LM authentication in Windows XP?

A.
Stop the LM service in Windows XP

B.
Disable LSASS service in Windows XP

C.
Disable LM authentication in the registry

D.
Download and install LMSHUT.EXE tool from Microsoft website

Explanation:
http://support.microsoft.com/kb/299656