Losing a Windows XP password is surprisingly common! Here are Fred's suggestions about how to get back into your accounts and files.
Lightweight Approaches: Resetting User Account Passwords
First, if you have access to any XP admin-level account on the machine in question, and need to gain entry to any other user account, the simplest method is via XP's built-in "userpasswords2" function: Click Start/Run, and in the Run box, type "control userpasswords2" without the quotes. A window will open showing you all accounts on the system. You can then use the "reset password" button to change any or all of the passwords on the system, even if you don't know the current password.
In some XP systems joined to Domains, and in some versions of XP Home, the direct approach of using "Control Userpasswords2" won't work. In these instances you have to edit the accounts conventionally via the Control Panel "User Accounts" applet, accessed from an admin-level account. This is less convenient, but still works fine.
The XP Help system and the Microsoft Knowledgebase both contain abundant additional information on this simplest form of resetting passwords. See these articles at Microsoft Service and Support".
Heavy-Duty Password-Resetting Tools
Ironically, Linux offers perhaps the easiest way to reset any XP account's password, including the Administrator account. (In XP Home, the Administrator account is normally so well hidden that many XP Home users don't even know that their system has an Administrator account, but it does.)
The tool can run from a floppy or CD, and is a series of highly automated scripts that lets you easily change the password of any user account on an NT/2K/XP box. You don't have to know the existing password to make the change, and the tool will even detect locked or disabled accounts and offer to unlock or re-enable them.
The "Offline NT Password & Registry Editor Bootdisk" is so well done that using it is often just a matter of accepting the defaults and hitting Enter when asked. But it's also flexible enough that you can break out of the automated process to accommodate whatever machine-specific idiosyncrasies you may encounter. Although the tool is almost two years old, the Web page still describes it as "very alpha," which I have to assume is the author's extreme programmatic conservatism because the software's never even hiccupped when I've used it. It's worked smoothly every time.
A similar Linux-based tool is the Trinity Rescue Kit http://trinityhome.org/trk/index.html , based on Mandrake 9.1. Broader in scope than the "Offline NT Password & Registry Editor Bootdisk," the Trinity Rescue Kit "... is designed to rescue/repair/prepare dead or damaged systems, be it Linux or Windows. It has networking capabilities like SSH, samba, and FTP and supports about every network card, disk controller, and USB controller. You can use it to repair a Windows 2000 or Windows XP system by setting the chkdisk flag or editing the registry or just reset the administrator password (or any other user). You can even undelete files from an ntfs, ext2, or fat partition ..."
Both the above tools are self-contained: You boot to the tool's own environment and work from there on the affected system. A somewhat less-direct option is the LAN-based freeware "NT Toolkit", a small suite of utilities optimized for password administration via a local network. The tools of primary interest are ServiceSecure ("allows you to reset service passwords by specifying the username and password rather than having to specify the service names themselves or changing the password manually"), and Password Assistant ("a GUI application that lets you update passwords of user accounts on multiple Windows NT, Windows 2000, or Windows XP machines. A good example is updating the Administrator password on all of your network workstations.")
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