How to freeze users in salesforce.com?

In salesforce.com, deleting a user is not possible. But the user can be deactivated by freezing that user in salesforce. To deactivate user go to Setup=>Administer=>Manage users=>Users=>Click on Freeze.

Hi,

From Setup, enter Users in the Quick Find box, then select Users.
Click the username of the account you want to freeze.
Click Freeze to block access to the account or Unfreeze to allow access to the account again.