There are a few softwares/tricks to log in to a Windows account if you don’t know the Administrator password. Most of them are boot CDs where you can boot up the computer and then change the password without knowing the current valid password.
DreamPackPL is a famous tool for this purpose.
But we have tools only for Windows XP

Kon-Boot is an prototype piece of software which allows to change contents of a linux kernel (and now Windows kernel also!!!) on the fly (while booting). In the current compilation state it allows to log into a linux system as ‘root’ user without typing the correct password or to elevate privileges from current user to root. For Windows systems it allows to enter any password protected profile without any knowledge of the password.

Kon Boot has been tested on:
Windows Server 2008 Standard SP2 (v.275)
Windows Vista Business SP0
Windows Vista Ultimate SP1
Windows Vista Ultimate SP0
Windows Server 2003 Enterprise
Windows XP
Windows XP SP1
Windows XP SP2
Windows XP SP3
Windows 7

Go to Download page here:
http://www.piotrbania.com/all/kon-boot/

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