Windows 7 - Accessing the Real Administrator Account

In Windows NT, 2000, and XP, there was an account named Administrator that was, by definition, a Computer Administrator account. You may have noticed that it’s nowhere to be seen in Windows 7. Actually, it’s still there, but hidden. There’s a good reason for this. It’s disabled by default and hidden on the Welcome screen and even in Safe Mode. And it requires no password to log on. This was done to provide a way to recover if you somehow manage to delete the last (other) Computer Administrator account from your computer. In this case, Windows will automatically enable the Administrator account so that you can log on (without having to remember a password) and re-create one or more Computer Administrator accounts, or turn a Standard User into an Administrator. (You would then immediately log off and use the restored regular account.)
This is a good fail-safe scheme, and we recommend that you leave it set up this way. Still, if for some reason you want to set a password on the Administrator account or use it directly, here’s how:

1. Click Start, right-click Computer, and select Manage.

2. Select Local Users and Groups, and open the Users list.

3. Right-click Administrator and select Properties. Uncheck Account Is Disabled and click OK.

4. Log off or Switch Users; then log on as Administrator (which now appears on the Welcome screen).

5. Press Ctrl+Alt+Del, and click Change a Password.

6. We strongly urge you to click Create a Password Reset Disk and make a password reset disk for the Administrator account. Be sure to store it in a secure place.

7. Back at Change a Password, leave the old password field blank and enter a new password as requested. Press Enter when you finish.

Now, the Administrator account is accessible and secured. If you’re worried that the default passwordless Administrator account is a security risk, remember that by default it can’t be accessed unless all other Administrator accounts have been deleted, and only an Administrator user could manage to do that. So, a non administrator can’t do anything personally to get to Administrator. If you enable the Administrator account, then, yes, you really must set a password on the account.

When you are logged on using the real Administrator account, User Account Control is bypassed, and all privileged programs run with elevated privileges.

Source of Information : QUE Microsoft Windows in Depth (09-2009)