I think it is not lost, you just forgot your password. To solve this problem, first you need to boot the system into Safe Mode.
1. Restart your system.
2. Press the ( F8 ) key about 3 times a second.
3. You should get the Windows startup menu. Use the (Up or Down) arrow keys to highlight (SafeMode)
4. Press (Enter) on (Safe Mode), then press (Enter) on (Windows XP).
5. The system should boot to Safe Mode.
Once you are at the Account Log on Screen, click on the icon for the user account with administrator rights, or click on the icon for the administrators account.
NOTE: For Home the Administrator account isn’t normally shown & in Safe Mode you have to press Ctrl+Alt+Delete keys twice to show. For PRO you can do this in normal mode
When the system has booted to the desktop, use the following steps to change the accounts password.
1.Click Start, Control Panel, Administrative Tools.
2.Click Computer Management.
3.Double click Local Users and Groups, double click the folder Users.
4.Right click on the account name that is locked out, and click on Set Password.
5.You may get a warning message about changing the password, simply click proceed.
6.Leave the New Password box blank, also leave the Confirm Password box blank.
7.Click OK, and OK again.
8.Then close all Windows, reboot the system and try to log in.
There are also applications that can recover the password for you. The following companies provide these applications at a cost.
iOpus® Password Recovery XP LostPassword.com
Asterisk Password Recovery XP v1.89
Windows XP / 2000 / NT Key
If the above information does not help in recovering the password, the only option left is to format the hard drive then reinstall Windows and the system software.