1) Click Start.
2) Click Computer (you might also find this icon on the desktop).
3) Right click on the Hard Disk icon where your OS is installed on and click Properties.
4) Click the Security tab.
5) Click the Advanced tab.
6) Click the Change Permissions button located after the Permission Entries list.
7) A new window will appear on your screen; which contains a list of all the User Accounts available on your computer.
8) Select the user account you want to give total control over your Windows 7) and click the Edit button.
9) Now, tick the checkbox labeled "Total Control" and press OK.