NOTE: This information is only for the password to login to the Windows 7 operating system.

If you have lost or forgotten your password for logging in to a computer running the Windows 7 operating system, there are a few different options:

If you have a password reset disk for Windows 7 have created, you can use that disk to reset the password for your account. For more information about creating and using the password reset on the Microsoft Knowledge Base:
How to create and use a password reset disk for a computer that is not a domain member in Windows 7
How to create and use a password reset disk for a computer in a domain in Windows 7

If you don’t have a password reset disk, the other option is to log on as the Administrator (or to have the person who is the machine’s Administrator log on) and change the password for your user account. For information on how to do this go to the following Mircosoft article:
How to Log On to Windows 7 If You Forget Your Password or Your Password Expires.

If you don’t know the Administrator password, and don’t have a password reset disk, then you will not be able to log on to Windows 7 , and will need to reinstall the operating system and recreate any user accounts.
There are some programs available on the web which claim to be able to reset the password(s) without access to an Administrator account, but these are not Microsoft programs, and are not recommended. If you do wish to try one of these programs (at your own risk), a web search should turn up a number of options.  Windows Password Key 8.0 is highly recommended.