It happens somebody graduates, somebody gets fired, somebody dumps you. Sooner or later, you may need to delete an account from your PC.

To delete a user account, open the User Accounts program, click the appropriate account name, and then click "Delete the account."

Windows now asks you if you want to preserve the contents of this person's Documents folder. If you click the Keep Files button, you'll find a new folder, named for the dearly departed, on your desktop. (As noted in the dialog box, only the documents, the contents of the desktop, and the Documents folder are preservedbut not programs, email, or even Web favorites.) If that person ever returns to your life, you can create a new account for him and copy these files into the appropriate folder locations.

The primary password that you or your administrator sets up in the User Accounts program has two functions. You already know that it lets you log on each day, so you can enter your Windows world of desktop clutter, Start menu tailoring, Web bookmarks, and so on.

But what you may not realize is that it's also the master key that unlocks all the other passwords associated with your account: the passwords that Internet Explorer memorizes for certain Web sites, the passwords that get you into shared disks and folders on the network, the password that protects your encrypted files, the password that protects your .NET Passport (and its Wallet for electronic payments, if you set one up), and so on. The simple act of logging onto your account also unlocks all of these other secure areas of your PC life.

But remember that anyone with an Administrator account can change your password at any time. Does that mean that whoever has an Administrator accountyour teacher, boss, or teenager, for examplehas full access to your private stuff? After you leave the household, company, or school, what's to stop an administrator from changing your password, thereby gaining access to your electronic-brokerage account (courtesy of its memorized Internet Explorer password), buying stuff with your Passport Wallet, and so on?

Fortunately, Microsoft is way ahead of you on this one. The instant an administrator changes somebody else's password, Windows wipes out all secondary passwords associated with the account. That administrator can log onto your account and see your everyday files, but not Web sites with memorized passwords, and so on.

Note that if you change your own passwordor if you use a Password Reset Disk, described in these pages none of this applies. Your secondary passwords survive intact. It's only when somebody else changes your password that this little-known Windows security feature kicks in, sanitizing the account for your protection.

If you click the Delete Files button, on the other hand, the documents are gone forever.

A few more important points about deleting accounts:

• You can't delete the account you're logged into.

• You can't delete the last Administrator account. One account must always remain.

• You can create a new account with the same name and password as one that you deleted earlier, but in Vista's head, it's still not the same account. As described in the box on the facing page, it won't have any of the original secondary passwords (for Web sites, encrypted files, and so on).

• Don't manipulate accounts manually (by fooling around in the Users folder, for example). Create, delete, and rename them only using the User Accounts program in the Control Panel. Otherwise, you'll wind up with duplicate or triplicate folders in Users, with the PC name tacked onto the end of the original account name (Bob, Bob.DELL, and so on)a sure recipe for confusion.

In previous versions of Windows, there's another kind of Administrator accountthe Administrator account.

This is a usually invisible, emergency, backup account with full administrator powers and no password. Even if you delete all of your other accounts, this one still remains, if only to give you some way to get into your machine. It's called Administrator, and it's ordinarily hidden.

Most people see it only in times of troubleshooting, when they start up their PCs in Safe Mode (page 656). It's the ideal account to use in those situations. Not only does it come with no password assigned, but also it's not limited in any way. It gives you free powers over every file, which is just what you may need to troubleshoot your computer.

The problem is, of course, that anyone who knows about it can get into Windows with full Administrator privilegesand no need to know a password. Your kid, for example, could blow right past your carefully established Parental Controls (page 361)and let's not even consider what a virus could do.

So in the more security-minded Vista, the secret Administrator account is still there. But it's ordinarily disabled. It comes to life only if (a) you're starting your PC in Safe Mode, and (b) if there are no other, real Administrator accounts on the machine.

(That's on a standard home or small-office PC. On a corporate domain network, only a networking geek who's got a Domain Admins account can start up in Safe Mode. You know who you are.)