If you cannot logon to Windows XP because you have forgotten your password, or it has expired, use your password reset disk:

How do I create and use a Windows XP password reset disk for a computer that is a member of a domain?

How do I create and use a Windows XP password reset disk for a computer that is NOT a member of a domain?

If you do NOT have a password reset disk:

1. If you have a local account, log on as a member of the Administrators group and reset the password:

        A. Open a CMD prompt.

        B. Type net user <UserName> <NewPassword>

2. If you have a domain account, a domain administrator can reset your password:

        A. Open a CMD prompt.

        B. Type net user <UserName> <NewPassword> /domain

NOTE: If an administrator resets your password, the following information will NOT be available:

1. E-mail messages that are encrypted with the user's public key.

2. Internet passwords.

3. Any files that the user has encrypted. The Recovery Agent must decrypt them.

If you have forgot the administrator's password, and using a null password doesn't work, see Another Windows NT password hack.