My situation is as follows:
1. I had Windows Vista, but did a full install using the upgrade 64-bit version of Windows 7 Home Premium. Microsoft will let you do this, but it takes about an hour on them with the phone as they verify your previous versions and painfully walk you through the process.
2. I then upgraded to Windows 7 Ultimate. That was a piece of cake (just type in the code).
3. The primary administrator account is turned off by default. No worries, as when I loaded, I did so using an administrator-level account I'd created and had been using daily for four months, now. I created a second administrator-level account as a backup, and wrote both usernames and passwords in a book I keep in the vault (requires both combo and a key to access it). Finally, I created a user-level account for both myself and my son.
4. Three days ago, I could no longer get into my either my primary or backup administrator accounts.
5. I poured over Microsoft's website, and they had more than a dozen different approaches to recover a lost administrator account, nine of which required you to log into at least some administrator account (duh!

).
A google search brought me here.
It's been three days, and nothing has YET worked. I am a retired Microsoft Certified Systems Administrator, and used to write for Network World about a decade ago.
I'm stumped.
Let me tell you what DOESN'T work:
First, try turning off UAC
If the solution is not solved by the previous postings, you can activate the true Administrators account by going to Start > Run and type cmd and hit Enter, then type the following:
net user administrator /active:yes
[/quote] Doesn't work from a user account. Error message: System error 5 has occurred. Access is denied. The second part of this approach (not mentioned by you, but by Microsoft) is to use the command prompt's net user commands to reset the password(s) of the other administrative accounts. Done it many times from Windows NT and XP, both workstations and servers. Not working here! Don't know if this will work on Windows 7, but here's a link to the Offline NT Password Recovery:
Link Removed - Invalid URL
It can be run from a USB or burnt to a CD.
No, it didn't work on Windows 7. I get a error message stating Volume has unsupported flags. I then typed the path to the SAM database it could not locate the registry directory.
Didn't work for me, either. I know of five different ubuntuu and Linux iso (boot disk) options which have worked on various versions of Windows in the past, all of which have supposedly been upgraded to, and tested on, Windows 7. Some try to recover the password. Two work to reset it to blank.
None worked for me.
Just ran into the same problem when I needed the administrator account because Adobe Reader install could not deal with my mapped directories. I actually just needed any account with default directories but administrator would do.
If you did not specify a password at install then apparently you cannot get into the administrator account - it will not accept your blank password field.
The fix is super-easy.
1. Type cmd in Start-Search
2. Right-click cmd result and "Run as administrator"
3. Enable administrator account if you have not aready done so by typing:
net user administrator /active:yes
Fail at this point. See System error 5 message, agove.
Here's what else I've tried:
1. Restoring from a system restore point, but it's not finding any. I thought they were enabled by default!
2. Password reset disk doesn't work.
3. Startup and restore finds nothing wrong.
5. Booting from the DVD/CD install disk and enabling the administrator account DOES work, and appeared to be the most promising, but apparently, booting it from the CD denies any further access to the hard drive. It shows only administrator and guest users. It will not allow me to create another administrative user on the hard drive, nor will any changes I make to the administrator.
I have to ask: Is this a case where Microsft was penny-wise and pound foolish, locking ALL back doors we've used in the past to get back into our systems, yet leaving the front door open for a hacker to change the admin passwords of my two admin accounts?
I'm beginning to think so!
If anyone has any other suggestions not previously mentioned, I'm all ears! Heck, I couldn't even tap into Microsoft's online help because it asks to install a program, and as you know, one can't do that from a normal user account.
"If all else failse, reinstall the operating system from scratch," right?
Nope. I tried that, as well. I can access the diagnostic and repair tools on the installation disk. No amount of cajoling will get it to offer me the installation option. When I try, it simply checks the hard drive for a valid copy of Windows 7, then says, "Windows 7 is already installed on this computer."
Anyone else feeling like Microsoft is really fighting back against that joke about "you're in a balloon?"