No administrator account?

Step 1:
Click start Control Panel. Select "User Accounts and Family Safety," then "User Accounts." Click "Turn User Account Control on or off." Remove the check mark next to "Use User Account Control (UAC) to help protect your computer." Click "OK." Set All Accounts to Administrator Still in the UAC section of Control Panel, select "Manage another account," and click on a user account. Click on "Change the account type." When working with multiple accounts, some changes can only be made if you and the account holder are both logged in with "Administrator" accounts so you need to change all user accounts to "Administrator." When you are done making changes, you can change them back to "Standard," but always leave at least one "Administrator" account. Select the "Administrator" radio button. Click "Change Account Type" at the bottom right. Repeat this procedure to change each user account to "Administrator." When all user accounts have been changed, close the Control Panel. Create a Full Administrator Account Click "Start" (the Windows Vista icon in the lower left of your screen). In the Search box, type "cmd". Right-click on "cmd," and select "Run as Administrator." An elevated command prompt window will appear. At the command prompt, type "net user administrator /active:yes", and press "Enter." Choose a password and assign it to the "Administrator" account, by typing "net user administrator 'password'", where 'password' is your selected password. For instance, if your password is "abc," type "net user administrator abc". Press "Enter." Type "exit" and press "Enter." Log off. When you log back into your "Administrator" account, you will have full rights.

Click start Control Panel. Select "User Accounts and Family Safety," then "User Accounts." Click "Turn User Account Control on or off." Remove the check mark next to "Use User Account Control (UAC) to help protect your computer." Click "OK." Set All Accounts to Administrator Still in the UAC section of Control Panel, select "Manage another account," and click on a user account. Click on "Change the account type." When working with multiple accounts, some changes can only be made if you and the account holder are both logged in with "Administrator" accounts so you need to change all user accounts to "Administrator." When you are done making changes, you can change them back to "Standard," but always leave at least one "Administrator" account. Select the "Administrator" radio button. Click "Change Account Type" at the bottom right. Repeat this procedure to change each user account to "Administrator." When all user accounts have been changed, close the Control Panel. Create a Full Administrator Account Click "Start" (the Windows Vista icon in the lower left of your screen). In the Search box, type "cmd". Right-click on "cmd," and select "Run as Administrator." An elevated command prompt window will appear. At the command prompt, type "net user administrator /active:yes", and press "Enter." Choose a password and assign it to the "Administrator" account, by typing "net user administrator 'password'", where 'password' is your selected password. For instance, if your password is "abc," type "net user administrator abc". Press "Enter." Type "exit" and press "Enter." Log off. When you log back into your "Administrator" account, you will have full rights.

Click start Control Panel.

Select "User Accounts and Family Safety," then "User Accounts."

Click "Turn User Account Control on or off."

Remove the check mark next to "Use User Account Control (UAC) to help protect your computer."

Click "OK."

Set All Accounts to Administrator

Still in the UAC section of Control Panel, select "Manage another account," and click on a user account.

Click on "Change the account type." When working with multiple accounts, some changes can only be made if you and the account holder are both logged in with "Administrator" accounts so you need to change all user accounts to "Administrator."

When you are done making changes, you can change them back to "Standard," but always leave at least one "Administrator" account.

Select the "Administrator" radio button.

Click "Change Account Type" at the bottom right.

Repeat this procedure to change each user account to "Administrator." When all user accounts have been changed, close the Control Panel.

Create a Full Administrator Account

Click "Start" (the Windows Vista icon in the lower left of your screen). In the Search box, type "cmd". Right-click on "cmd," and select "Run as Administrator." An elevated command prompt window will appear.

At the command prompt, type "net user administrator /active:yes", and press "Enter."

Choose a password and assign it to the "Administrator" account, by typing "net user administrator 'password'", where 'password' is your selected password. For instance, if your password is "abc," type "net user administrator abc". Press "Enter."

Type "exit" and press "Enter."

Log off. When you log back into your "Administrator" account, you will have full rights.

hope this helps

Click start Control Panel.

Select "User Accounts and Family Safety," then "User Accounts."

Click "Turn User Account Control on or off."

Remove the check mark next to "Use User Account Control (UAC) to help protect your computer."

Click "OK."

Set All Accounts to Administrator

Still in the UAC section of Control Panel, select "Manage another account," and click on a user account.

Click on "Change the account type." When working with multiple accounts, some changes can only be made if you and the account holder are both logged in with "Administrator" accounts so you need to change all user accounts to "Administrator."

When you are done making changes, you can change them back to "Standard," but always leave at least one "Administrator" account.

Select the "Administrator" radio button.

Click "Change Account Type" at the bottom right.

Repeat this procedure to change each user account to "Administrator." When all user accounts have been changed, close the Control Panel.

Create a Full Administrator Account

Click "Start" (the Windows Vista icon in the lower left of your screen). In the Search box, type "cmd". Right-click on "cmd," and select "Run as Administrator." An elevated command prompt window will appear.

At the command prompt, type "net user administrator /active:yes", and press "Enter."

Choose a password and assign it to the "Administrator" account, by typing "net user administrator 'password'", where 'password' is your selected password. For instance, if your password is "abc," type "net user administrator abc". Press "Enter."

Type "exit" and press "Enter."

Log off. When you log back into your "Administrator" account, you will have full rights.

hope this helps

Once you have deleted it, its gone.
If your login has administrator's rights, then you can create a new administrator user or any other username.
Go to Control panel - User Accounts to create a new user

Dear Friend,
There is one default account in system by name Administrator. Log from that account. (Administrator account is having all rights to perform any process in the computer.)
Or you can do delete all your user account so only administrator account will remain. Then Log off.. and while login you will able to see that account.
Please rate the answer.

sign in using his name and password if it is using one  then go to control panel/user accounts and change your name to administrator  then boot back to your user name

start bar/settings/control panel/user accounts/ delete what you want

Boot into safe mode (F8 on startup) and let windows load, look under Users and you'll find your account has magically reappeared. Change the Sellers account back to an administrator and then reboot. Your account will then be visable again on normal boot up.

Power up your 'puter and press f8 to enter windows in safe mode.When it boots into safe mode go to your start button... select control panel.. and find user accounts . Enter and make yourself a new user account.. select administrator account . Close and and reboot the computer. Select your new user account and it should boot into windows. Go back to user accounts and you should see your account.. a guest account.. and the account of whoever owned the computer before you . That account will say password protected. select delete user account and click on the old users account . Windows will say it will delete the account and all files of the user. if it asks select ok and be patient . It will be a few minutes as windows deletes the account. Do a final reboot and the old account and password should be gone.
Good luck.
Don