Best way to make it so an exe can only be run once

Private Sub Form_Load()
    If App.PrevInstance = True Then
        MsgBox "Already running"
        'Do whatever you need to do before closing
    End If
End Sub

private bool CanIStart
{

    	try
    		{
    			MyAppMutex= new Mutex(false, "myAppMutex", out createdNew);
    			if(MyAppMutex.WaitOne(0,false))
    			{
    				return true;
    			}
    			else
    			{
    				MyAppMutex = null;
    				return false;
    			}

    		}
    		catch(ApplicationException ex)
    		{
    			// we couldn't create the mutex. // log the error if you care
    			return false;
    		}
}

' Test eventual mark, settings in the registry.
if GetSetting("MyInstallerApp","Startup","BeenHere",0) = 1 then
    MsgBox "This installer was ran once already... first run the un-installer."
    End ' or some other code to properly exit the installer
EndIf
Call SaveSetting ("MyInstallerApp","Startup", "BeenHere", 1) 'leave a mark for future

' Allow future Installer to run again
Call DeleteSetting("MyInstallerApp", "Startup")