Run this program as administrator

Look for an option at the bottom of that screen to "Change settings for All Users" and click it.  You should get the same dialog box that you can uncheck.
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Here's a better screenshot.
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Also, are you logging in as the true Administrator, or as an account with Administrator privileges? You may want to try to login as Administrator, to make the changes.
http://www.vistax64.com/tutorials/67567-administrator-account.html

Here is an article written by: EE Expert Alex W:
Here is the link:             Use the Administrator account by default in Win7 and Vista
       
Here is the article in-case you can't go to the article:
          Community Pick    

Are you annoyed by all the restrictions Vista and Windows 7 places on  the default user?  Your user privileges are restricted which can result  in unexplained errors when you try and do things unless you figure out  that it’s all to do with your user rights.  In a business environment  this may be the intention (to control what users do) but at home you  would normally want to do whatever you want.

Using Administrator privileges, however, can be risky  based on your PC knowledge because you will be allowed to do anything  you want, including mess things up by mistake!  Before continuing, make  sure you are happy with having 'god mode' on your PC and that you, or  anyone else, is not liable to go doing things that would adversely  affect your PC.

[Ed. Note:] Also, if you are ever hit by a virus or other malware, that code will run with full administrative privileges; it  gets to run in 'god mode.'  It can install device drivers, usurp  system-critical functions, write anything it wants anywhere in the  registry, send emails containing your banking logon information to  someplace in Russia... In short, it can kill your computer, laughing at  you as it does so.  So consider this a friendly "head's up!"

Here  is how to enable the Administrator account, set it to automatically  login as Administrator and then remove your original user account if not  needed.

1. Open your start menu and  in the ‘Start Search’ box at the bottom type “Command Prompt”.  You  should see the command prompt at the top of the start menu.  Right click  and choose ‘Run as Administrator’.  The command window will appear with “Administrator: Command Prompt” in the title bar.
2. Activate the administrator account by typing: net users Administrator  /active:yes exactly as shown, i.e. capital A, spaces etc.  Hit enter and you should see "The command completed successfully."
3. Log-off  and you should now see ‘Administrator’ log-in as an option.  Choose to  log-in to Administrator (this may take a while because logging in for the  first time under any user will go about creating your documents  folders.  You should now see ‘Administrator’ as your documents folder  name (top right of the start menu under the picture).
4. Now set Administrator as the default Windows user.  Bring up the Run window by holding the Windows Key and press R.  Type: control userpasswords2 and  hit OK. This should open the ‘User Accounts’ window.  To bypass the  login screen uncheck the box that says “Users must enter a user name and  password to use this computer.”  Now a window titled “Automatically Log  On” will appear allowing you to specify credentials so windows can  login automatically. The user name should already have ‘Administrator’  and you can leave the password boxes blank if you haven’t set one up  since enabling it.
   NOTE: if you want to set a password for the Administrator account to use you can go Start > Control Panel > User Accounts > ‘Create a password for your account’. This should be entered on the ‘Automatically Log On’ dialog box above so auto-log-on can take place.
   WARNING:  if you remove your old account, your documents folder associated with  it will go as well!  Make sure you move everything you want to keep over  to the Administrators documents folder.
5. If  you’re now only going to use the administrator login, you may want to  remove your old redundant login account to restore hard drive space.  Go  into ‘User Accounts’ same as above but choose ‘Manage another account’,  click on your old account and choose ‘Delete the account’ from the  left.  Here you can choose to keep or delete the users files (make sure  you backup what you want to keep) then hit ‘Delete Account’.
   

That’s  it!  No more access denied messages; when you boot up, Windows will  bypass the login screen and automatically start you as the  Administrator.