I would like to change my account from my Grandson' name x my name z am having trouble using my original user name & password.

No - he has to sign in with your info - once in he can make changes.

You need to restart with original media disk and then you can choose reset password from the apple menu bar.

you don't need to unsubscribe. The person who has the account name and the password, is the only one who can access. If you want to stop using the account it would be wise to delete everything in the site first.
Then depending on what account is was, shut it down and never use it.
Perhaps your grandson already took over your account, without telling you, and then you won't be able to delete anything. Just setup a noter page with your name and your own password. Don't tell anyone your password, or you risk the next account to be hacked too.

Resetting a password without an additional account Use these steps to reset a password when there is only one administrator account on the computer, or if the original administrator account needs a password reset.
"Original" administrator account refers to the one that was created immediately after installing Mac OS X. If the original administrator password is known, that administrator account may be used to reset the passwords of other administrator accounts using the steps described above. These steps require an optical drive; if your Mac does not have an optical drive and you have a Mac OS X v10.6 Install disc, see below.

1. Start up from a Mac OS X Install disc (one whose version is closest to the version of Mac OS X installed). Usually, you can start from the disc by putting it in your computer, restarting, and holding the C key. Or, put it in the computer and click the Install or Restore icon you see in the disc's main window (after which the computer will start from the disc without you needing to hold C). Or, you can use Startup Manager or the Startup Disk preference pane to select the Install disc.
2. Choose a language, click the arrow button to continue,
3. Mac OS X v10.6 or later: Choose Password Reset from the Utilities menu.
   Mac OS X v10.5 or v10.4: Choose Reset Password from the Utilities menu.
   Mac OS X v10.3: Choose Reset Password from the Installer menu.
   
   Tip: If you don't see this menu or menu choice, you're probably not started from the disc yet.
   
   Note: The default keyboard layout is U.S. English while started from the installation disc. If you use a keyboard layout other than U.S English, use the Input menu (the flag icon on the right side of the menu bar) to select the desired layout before typing a new password.
4. Select your Mac OS X hard disk volume.
5. Select the user name of your original administrator account.
   
   Important: Do not select "System Administrator (root)". This is actually the root user. You should not confuse it with a normal administrator account.
   
   >
6. Enter a new password.
7. Click Save.
8. Click the red button in the upper left corner to quit the application.
9. Choose Quit Mac OS X Installer... from the Mac OS X Installer menu.
10. Click Restart.

After following these steps, you need to update your keychain so that it recognizes the new password.
If your computer doesn't have an optical drive, connect it to a computer that does using Target Disk Mode, or use the Remote Install Mac OS X utility to start up the computer remotely. Resetting a user's password in Mac OS X v10.5 or earlier If you are using an earlier version of OS X, select your version number below for password reset instructions. Avoid setting a blank password for a user account when using these steps. Mac OS X v10.3 through 10.5.8

1. Log in with an administrator account. Tip: If you don't know the password of any administrator accounts, see "Resetting the original administrator account password" above.
2. From the Apple menu choose System Preferences.
3. From the View menu choose Accounts.
4. Click the lock button if it appears locked; enter the administrator password.
5. Select the name of the user whose password you want to change.
6. Click the Reset Password button or the Change Password button.
7. Enter a new password in both the New Password and Verify fields, and add a Password Hint if desired.
8. Click the Reset Password button or the Change Password button.
9. If a dialog box appears with the message "Your Keychain password will be changed to your new account password," click OK.

Mac OS X v10.2 through v10.2.8 Use Accounts preferences to reset an account password.

1. Log in with an administrator account. Tip: If you don't know the password of any administrator accounts, see "Resetting the original administrator account password" above.
2. From the Apple menu choose System Preferences.
3. From the View menu choose Accounts.
4. Click the lock button if it appears locked.
5. Select the username whose password you want to change.
6. Click Edit User.
7. Navigate to the New Password field.
8. Enter a new password in both the Password and Verify fields.
9. Click OK.
10. If a dialog box appears with the message "Your Keychain password will be changed to your new account password," click OK.

Regardless of how many characters are actually in a Mac OS X v10.2 password, seven bullet characters (•••••••) will appear in the New Password and Verify fields the next time the password is edited. Mac OS X v10.1.5 or earlier Use the Users preference pane to reset a the password.

1. Log in with an administrator account. Tip: If you don't know the password of any administrator accounts, see "Resetting the original administrator account password" above.
2. From the Apple menu choose System Preferences.
3. From the View menu choose Users.
4. Click the lock button if it appears locked.
5. Select the username whose password you wish to change.
6. Click Edit User.
7. Enter a new password in both the Password and Verify fields.
8. Click Save.

Important: Passwords for administrator accounts should not be blank.

Regardless of how many characters are actually in the password, thirteen bullet characters (•••••••••••••) will appear in the Password and Verify fields the next time the password is edited.

You need to change the user name and password from your grandson to new ones for you.

YOU WILL ALWAYS HAVE AN ACCOUNT WITH YOUR INTERNET PROVIDER AND PASSWORD,

YOU WILL NEED TO SET UP A SUB ACCOUNT, WHICH IS A SECONDARY ACCOUNT ASSOCIATED WITH YOUR MAIN INTERNET PROVIDER. EACH SUB-ACCOUNT HAS ITS OWN UNIQUE USER NAME AND PASSWORD.

GO TO TOOLS, UNDER ACCOUNTS, SET UP YOUR NEW EMAIL ACCOUNT, USER NAME AND PASSWORD

ARE YOU WANTING TO USE LIKE A YAHOO ACCOUNT? IF SO MAKE SURE YOU HAVE TRANSFERED YOUR OLD ACCOUNT INFORMATION & CONTACTS FROM YOUR LAST EMAIL PROVIDER INTO YOUR NEW ACCOUNT...AFTER YOU SET UP YOUR NEW ACCOUNT INFORMATION...GO TO TRUESWITCH.COM TO TRANSFER ACCOUNT INFO, ETC,.

HOPE THIS HELPS!

Assuming you are using Windows 7, go to control panel, manage accounts, name of account to change. The top two options should be "Change the account name" and "Change the password". The procedure should be similar for Windows Vista and XP, but if it's not, please specify.

Reset
Pressing the Reset button for 5 seconds restores the router to its original factory default settings.

Log in to the Router
This section will explain how to log in to your router using the following steps:
1. Launch your web browser.
2. Enter the URL http://192.168.1.1 in the address bar and press Enter.
A login screen like the one below will be displayed after you connect to the user interface.
Note: There are three account types, each requiring a different username and password.
• The user account provides limited access to certain configurations (username / password: user / user).
• The admin account can perform all functions
(username / password: admin / admin).
• The support account is for ISP technicians for maintenance purposes
(username / password: support / support).
Note: Passwords can be changed at any time.
3. Enter your user name and password, and then click OK to display the user interface.
Note: This manual has been prepared using the admin user name

Visit the Google Accounts: Password recovery page located at:
https://www.google.com/accounts/ForgotPasswd?service=mail&fpOnly=1

• Google states that there are no registered user accounts that match that name.

Are you sure that is your correct email address/username?

Look at your recently sent mail items, open a message you have sent, double-click on your name/email and verify that you have the correct email address information.

If it what you have typed in the original post them you will need to register as a new account using the email you provided above.

Here what u can do,
has soon as the computer restarted and u see yr grandson screen just press alt,ctrl and del 2 or 3 times and it will prompt u for and administrator password u can either enter the administrator password or u can changed the user name from administrator to yrs and just enter yr password that u normally use..that should do the trick ok..