You must have somehow created a password when installing Windows. If you set up your account as a limited account, choose Change Account type and make it an Administrator. I that doesn't work:
To enable the hidden Administrators account:
Go to Start > Run and type cmd and hit Enter.
Now type in the following:
net user administrator /active:yes
To disable it type
net user administrator /active:no
If that fails to work, you can use a password dumping tool for ethical purposes. It's called pwdump3e. It must be run from the command-line and have at least two accounts enabled.You can download it here:
http://www.openwall.com/passwords/dl/pwdump/pwdump3e.zip You could alos run this registry script that will enable you to take Ownership of a complete directory:
Copy and paste the info inside the quote into Notepad, choose Save As, then select All Files from the drop-down menu box and type in takeownership.reg. Save it to your desktop and double-click on it to merge it intro the registry. this will place Take Ownership to the right-click context menu for folders.
[HKEY_CLASSES_ROOT\Directory\shell\runas]
@=\"Take Ownership\"
\"NoWorkingDirectory\"=\"\"
[HKEY_CLASSES_ROOT\Directory\shell\runas\command]
@=\"cmd.exe /c takeown /f \\"%1\\" /r /d y && icacls \\"%1\\" /grant administrators:F /t\"
\"IsolatedCommand\"=\"cmd.exe /c takeown /f \\"%1\\" /r /d y && icacls \\"%1\\" /grant administrators:F