To delete a user you first have to select him or her using the the "edit" link. Once the user information is loaded into the form you should see a "delete user" button at the bottom of the screen. Once you click on it the system will check to see if the user has any active records that are waiting for approval or pending submission. If not, it will allow the deletion to proceed. If it does find some records it will give you a warning message and suggest that you simply de-activate the user instead.