There are only two ways to regain access to your PC if you've forgotten your Windows Administrator password. The first is to reinstall Windows and totally wipe everything from your computer … and the second is to use a "password reset" program that will reset the password for you. Here's what to do:
Method 1 – Reinstall Windows – If you've got nothing to lose from your computer, and have the knowledge to do it, you may wish to reinstall Windows to gain access to your PC again. The only problem with this method is that reinstalling Windows literally means you will lose every file and every piece of data on your PC. This is okay for some people and if you are interested in using this method, you simply need to insert the Windows disc into your PC, reboot your system and select "Boot From CD" in the BIOS options. If you do not understand how to do it, then you need to talk to a computer technician.
Method 2 – Use Password Reset Software – The most common way to restore access to your PC is to "reset" the Administrator password for your system by using a piece of "password reset software". These programs have only recently started to hit the mainstream, but they are actually extremely effective and easy to use.
Basically, password reset software is a program is that runs before Windows loads and then changes the stored passwords on your hard drive. We're fortunately in that Microsoft has not changed the way which Windows stores passwords through the evolution of the system, and even in Windows 7, passwords are kept inside a series of files and settings on your hard drive. The various password reset programs that are now available basically go through these files and change them to remove the password on your PC and allow you to log in again.
To use one of these tools, you basically need to download one of the Internet onto a computer that you do have access to (such as this one). It will then create a CD for you, which you should put into the PC that is locked. The locked PC will then load up the program on the CD before Windows, which will then change the various files and settings that are storing the password for your PC. After that, it will restart your system and Windows should load up normally again, logging in straight away.