As in Windows XP, Administrator account is not enabled by default in Windows 7.It is designed to protect your system from inadvertent or malicious incidents that could compromise stability or security while you are logged on using an account with administrative privileges, where you have full access to the system. Even when your administrator account is not enabled in Windows 7, you can always perform administrative operations by working through the UAC prompt. But there are time
when you need to be logged on as Administrator to perform some tasks. Here we will go through the tutorial on how to enable Administrator account.

Warning: Do not make your Administrator Account default login, use below technique on your own risk.

Step I - Right Click on computer > and click on Manage as shown below

Step II - Navigate to Local users and groups and than to users as shown below

Step III - Right click on Administrator and than to properties as shown below

Step IV - Untick account is disabled option and click on OK. 

Step V- your Administrator account is enabled now. By default Administrator account has blank password, your next step will be to set a password — preferably a complex password consisting of at least eight characters and using uppercase, lowercase, and numbers or special symbols.
     
        Follow following steps to set a password on your new Administrator account

Step VI - Right click on Administrator and than click on set password as shown below

Step VII - You will be shown a warning that explains that resetting a password from outside the account itself can cause irreversible loss of information However, since the Administrator Account has never been used, you can click Proceed as shown below

Step VIII - Set password and confirm password.

Step IX - You have now activated the administrator account with password. When you logoff your PC you will see user icon for administrator account, just click on Administrator icon and supply password to be logged on as Administrator.