Incorrect placement of data with the modules?

I under stand the process as follows: target converted to lead converted to contact, opportunity associated with contact. My question is how do you prevent information from being entered into a lead once it is converted to a customer? I worry is that a contact which is the last stage in the game someone will accidentally place notes or history under their lead information.

would there be a way to remove or hide the data once they are converted. what I mean:

Once a target is converted to a Lead that Target is hidden or removed from the Target module or Target List.
Once a Lead is converted to a Contact that Lead is hidden or removed form the Lead module or Lead List.
The Contact would be the last step in the process for us.

Thank you for you insight into my concerns. It is very mush appreciated.

In admin section, System Settings, you have some option to choose.
Lead Conversion Options: Information
Disable convert lead action for converted leads:

Another solution is :


overide detailview

Then verify if it’s converted or not… i think you have all info (contact_id, account_id and status) in the bean.
if yes, redirect to the linked contact or account.

$queryParams = array( 
    'module' => 'CustomModule', 
    'action' => 'DetailView', 
    'record' => $recordId, 
SugarApplication::redirect('index.php?' . http_build_query($queryParams));