You can try logging on with the built-in Administrator account
and going to Control Panel -> User Accounts to change the
password.

How you log on with the Administrator account depends on what
version of XP you have installed on your computer.

XP Home Edition

To logon with the built-in Administrator account in XP Home
Edition you have to restart the computer and boot into Safe
Mode.
To start in Safe Mode, reboot your computer and
start tapping the F8 key as soon as you see anything displayed
on the screen.
Keep hitting F8 until the Advanced Startup
Options menu appears.
Use the up and down arrow keys on your
keyboard to select Safe Mode.
Hit Enter.
Click on the Administrator icon.
Unless you changed it, the password should be blank.

XP Professional
Restart your computer.
If the Welcome screen is displayed, hit the Ctrl + Alt + Del
key combination twice.
This should bring up the Log on to Windows dialog.
Enter Administrator in the User Name box.
If you set up a password for this account, enter it now.
Otherwise, leave the password box blank.

If you're still locked out of your computer, take a look here.

Offline NT Password & Registry Editor
http://home.eunet.no/~pnordahl/ntpasswd/

Ultimate Boot CD for Windows®
http://www.ubcd4win.com/howto.htm

Good luck

Nepatsfan

You could also try a program called 'ophcrack' available from
www.sourceforge.net.

This will allow you to create a bootable Linux CD that can retrieve your
password.

HTH

Neil
www.nwarwick.co.uk

    Simply log in using the built-in Administrator account (which
cannot be deleted) and modify the desired account(s) and use Start > Run

    By design, the only way to log into the Administrator account of
WinXP Home is to reboot into Safe Mode.  For WinXP Pro, pressing
CTRL+ALT+DEL twice at the Welcome Screen will produce the standard login
dialog box.

    Unless you've set the Administrator's password via the Management
Console (_not_ the Control Panel), it's probably still blank.  WinXP Pro
asks the user to set the Administrator's password during installation,
but WinXP Home doesn't.

How to Log On to Windows XP If You Forget Your Password or  Your
Password Expires
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q321305

    Failing that, Linux-based password cracking utilities abound on the
Internet, freely available to anyone who can use Google.