How to login as Administrator in Windows XP and Vista?

In Vista:

First you must to enable “Administrator” account in your OS.

My Computer (right click) –> [Manage] –> [Users and Groups] –> Users –> Administrator –> Properties.

Then do the same thing as WinXP do.

In WinXP:

Method 1: Using TweakUI Power Toy for Windows XP

Download TweakUI from here:

Open TweakUI and click “Logon” option in the left pane. Put a checkmark against the option “Show Administrator on Welcome Screen”. Click OK to close TweakUI. Logoff and see if Welcome Screen lists Administrator login. Changes are immediate and you can use the Winkey + L to switch back to Welcome Screen to see Administrator account is listed.

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Method 2 - Manual registry edit

• Click Start, Run and type Regedit.exe

• Navigate to the following key:

HKEY_LOCAL_MACHINE SOFTWARE Microsoft Windows NT CurrentVersion Winlogon SpecialAccounts UserList
 

• Use the File, Export option to backup the key.

• Right-click in the right pane and select New DWORD Value.

• Type-in Administrator as the value.

• Double-click Administrator, and assign a value of 1

• Close Regedit

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Reference:

http://windowsxp.mvps.org/admins.htm