The latest versions of Windows has a feature called 'Reset Disk' which creates a disk (whether it is floppy disk or other kind of disks) allowing user to reset one's login password.
Most users are not aware of this feature until they actually forgotten the password to their PCs and they ended up searching online for answers.
Creating the 'Reset Disk' is easy.
In fact you'll be guided on how to do that in Windows Vista or Windows Seven but unfortunately once you have forgotten your password the system won't allow you to do this.
This feature will only be accessible if you still remember your password by any means if you forgot your password later you can use this created disk to recover it.
Consequently, if you haven't forgotten your password; you can do so by going to the control panel and create your password reset disk.
Another way to recover your password is via safe-mode.
However this is only an option if you have to or more administrator accounts; and you need to be able to access either one of those accounts.
(Or you need to have the access to administrator account which is hidden in the safe mode) All you need to do it boot up your PC and enter the safe-mode.
Once you are in the safe-mode; login with your Administrator account and pretty much you are free to reset passwords to other user accounts.
There is one last way to do it but it is not easy.
It involves hacking and pretty much could ruin your computer if not done correctly.