Many time you might need to access a system but have been locked out or the password to access the local system has been forgotten. There are many ways to deal with that.

NT Offline
If you just want to get in quickly you can use NT Offline. NT Offline will allow you to blank/clear or change the password of an existing local account.  This boots up in to a linux command line utility.  From here you select the drive the OS is on, the path to the config files, and then which account(s) you would like to modify.

fgdump
Being able to change  a password is great and all but what if you need to get the password.  fgdump will allow you to dump the dump the LSASS.  This will allow you to get the users accounts and their hashed passwords.  How to find the password from the hash is another story.  You might start by looking at RainbowTables.

KonBoot
This is the new tool.  It is getting quite a bit of hype right now.  This tool will boot a different kernel of the OS and then load Windows or Linux during the boot.  Once you get to the login screen, simple select a local user or a cached user and press enter with no password and you are in.  There is not much you can do to the account, but you have access to the machine.

Yes I know that these can be listed as “hacker” tools.  But the “hacker” tools are a administrator’s best friend.

I will post these in the links section also.