You probably know about the "hidden" administrator account in Windows XP. It's the only account on XP systems on which no other accounts have been created.
Until you add a new account, you zip right to the desktop when you boot the OS, with no stop at the Welcome screen. Once you set up one or more new accounts, the default administrator disappears, though you can bring it back in both XP Home and Pro. (More on this below.)
Windows Vista ships with this account disabled, which is not such a bad thing because every user on the PC should have his or her own custom account, even if "every" translates to "one."
Still, this back-up administrator account can come in handy if you encounter some problems logging into or otherwise using Vista. To enable it, right-click the Command Prompt on the Start menu (it is likely listed under Accessories), choose Run as administrator, type net user administrator /active:yes, and press Enter. You should see a message stating that the command completed successfully. Type exit and press Enter again to close the Command Prompt window.
When you restart Windows, you'll see a new account labeled simply "Administrator." The first time you log into this account, Windows will tell you that it's preparing the desktop before the system's default desktop appears. Click Start > Control Panel > User Accounts and Family Controls > Change your Windows password > Create a password for your account, enter your password twice, add a hint (if you wish), and click Create password. (If you use Control Panel's classic view, the settings to create a password are in the User Accounts applet.)