Ok, so you say you forgot your Windows administrator's password, huh? Oh well, it doesn't really matter if you did or you just say you did. The fact is that you need to gain access to a computer and you cannot "remember" the administrator's password. How can you get out of this situation without formatting and re-installing the operating system?
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One method of gaining access to the system is by trying hard to remember the forgotten password, or a password of another user which has the same level of administrative rights. However I don't think this approach will help you, otherwise you wouldn't be sitting here reading article, would you?

Another method is by trying to restore a backed up System State (in Windows 2000/XP/2003) or a ERD (in NT 4.0) in which you do remember the password. The problem with doing so is that you'll probably lose all of the recently add users and groups, and all the changed passwords for all of your users since the last backup was made.

A third method might be to install a parallel operating system on a different partition on the same computer, then use a simple trick to gain access to the old system. Read more about it on my Forgot the Administra