For customer activation please install following free extension from GitHub:
After installation go to System > Configuration > Customer Configuration. You will see new block of settings at the bottom.
Customer activation parameters
Turn extension on/off. You can configure activation for Store View and create special site section for specified customer group that requires activation.
Notify Admin on Customer Registration
Send notification e-mail on new customer registration.
Admin Email Address
E-mail address for admin notification.
Admin Notification Email Template
Select notification template to format notification e-mail to your needs.
Notify Customer of Account Activation
Send notification e-mail to customer regarding his account activation.
Activate new Customer Accounts by Default
Select if you wish all new customer accounts to be activated on registration.
After customer registers he will see a warning when trying to log in the account area.