Re-set Your Admin Password With a Bootable Windows CD-ROM
Step1
Modify your PC's BIOS so that it will boot from the Windows CD-ROM. Insert the Windows CD into the drive and boot up the PC. Watch the screen messages until you see the prompt: "Press any key to boot from CD."
Step2
Go through the boot-up process until you get to the "Setup" screen where you have the option to install or repair. Choose the option to repair and press "R" which will launch the repair process. As the repair runs, Windows Set up will do a check on your disks and then begin to copy files. This may take a few minutes. Your PC will then re-boot itself automatically.
Step3
Open a command prompt after your PC reboots and resumes set-up. Here's how:
* In Windows 2000, wait until the point where it's registering components, and then pres the "Shift + F10" keys.
* In Windows XP, watch the bottom left-hand side of your screen until you see a progress bar that reads: "Installing devices," and then press the "Shift + F10." This will open a command console.
Step4
You can now gain access to your Control panel. Here's how:
* In Windows 2000, enter this command: control.exe
* In Windows XP, type: nusrmgr.cpl
* Press "Enter," and you will have access to the control panel.
Step5
Use the tools provided to reset your passwords. When you are done, close the control panel and then type in "Exit" to close your command console. Allow the repair to complete as usual. You will then be able to log on using your new password.
Alternative ways to Access your PC
Step1
Log into another administrative account on the same computer, if you have one. Reset the password for the account whose admin password you lost. Log out and log-into your administrative account. This simple method of resetting an administrative password makes it highly advisable to have two admin accounts on a PC if there is a chance you may forget the password.
Step2
Disconnect your hard drive and re-install it on another PC as a slave drive. Using this method, you will be able to access the files that you had stored on the account whose admin password you lost.
Step3
Re-set your password using third-party software such as the Offline NT Password and Registry Editor by Petter Nordahl-Hagen (See Resources below). This application gives you access to accounts on Windows 2000, Windows XP, Windows Vista, Windows Server 2003 and NT systems.
You can access your PC even if you forget your administrative password
Novice 
Comments
aannggiieess said
on 4/14/2008 Another way to bypass it is at the login screen, press Ctrl + Alt + Del twice and it will let you type in your username. You can then type "Administrator" and access the hidden admin account. The only problem with this and the safe mode option is that you CAN have an administrator password. It is an option you set in setup, but most people don't, and computers don't come factory installed with admin passwords.
advertiser said
on 4/14/2008 Thats a way too long process... Normally when you first install assuming its windows XP or Vista, you will create an administrator account before creating other user accounts. This administrator account is by default "no password" unless you specify otherwise. Anyway, heres how you do it.
1. Reboot the computer and begin tapping F8.
2. Choose Safe mode.
3. On the logon screen, click on administrator.
4. Go to start>control panel> user account
5. Choose your account and then remove and add a password. and viola! its all done.