Windows log-on password is helpful and necessary in preventing unauthorized access.

The Windows log-on password comes in handy if you do not want intruders
or unauthorized users to log onto your computer and make system
changes, delete files or install applications without your permission.
When you set the password, Windows prompts you to enter it each time
you restart or log off Windows. Therefore, it is very necessary to set
such a password for your computer.

Setting more than one Windows log-on user accounts can be helpful before you forgot Windows password.

Usually computer users are highly recommended to set two or more user
accounts for their computers, having at least one administrator user
account. This can bring convenience if your roommate or family members
share your computer and it also can prevent your computer from being
locked when you forgot Windows login password.

What to do when you forgot Windows admin password if on other user account on your computer?

The thing is that some people may just have one Windows login user
only for their computer. At this time, if Windows password is
forgotten, it would be very likely to lose access to the computer for
many users. So is there any way or solution to solve this problem?
Fortunately, many third-party applications are available that can help
you

Break Windows Password with Windows Password Reset Std.

Step1: Download Windows Password Reset Std and install it to another accessible computer properly.

Step2: Run this program and insert the CD/DVD to this computer, and
then click “Burn CD/DVD” button to start burning an ISO image file to
the CD/DVD.

Step3: After finishing the burning, remove the CD or DVD from the
computer and then insert this CD or DVD to the locked computer.

Step4: Set the locked computer to boot from CD/DVD in BIOS.

Step5: Start to recover forgotten Windows password
with burned CD/DVD with only 3 clicks of mouse. Then in less than 1
minute, you will regain access to your PC without a password.

One more tip: unlock Windows password
by reinstalling system with the Windows installation disk is another
way. But I do not recommend this since you would lose lots of data on
your computer. While using this tool—Windows Password Reset Std can
well help reset forgotten Windows password.

Source: http://www.windowspasswordreset.net/article/forgot-windows-password.html