So I'll try to explain. Below are two ways to get in if no Hidden admin p/w is assigned. They accomplish the results just a different way to go about it.See the note at the end of #1 to assign a p/w to the hidden admin account.
NOTE: If the hidden admin account (Safe Mode) is password protected you will need that password to use this procedure.
Boot to the sign in screen.
In the box that pops up type Administrator for the User name
leave the password blank and click OK or press Enter.
Windows will boot the hidden admin account.
Open Control Panel---User Accounts.
Open the account you are locked out of.
Click Remove Password//Change password
Close out the open windows and Reboot.
If that is the only account you have windows will boot to your desktop. If there is more than one account just click the previously locked account.
NOTE: If you can break into your computer using this method you may want to make a Password for the Hidden Admin account while in Safe Mode. Jot the P/W down and put it in a safe place in the event you need it again.
Lost password, Change Password or Delete Password on XP User Accounts with Admin or limited Privileges.
This procedure only works if you can enter safe mode thru the hidden Admin Account
1-Boot to Safe Mode by tapping the F8 key while booting
2-Choose safe mode, Press Enter
3-Select operating system, Press Enter
4-Click Administrator Account
5-Windows is running in Safe Mode, Click YES
6-At the Safe Mode Desktop, click, Start, Control Panel
7-Double click User Accounts, Here you can delete accounts, delete/change passwords ETC.
8-When done Close all Windows