Main menu block exits in plugins list, cann't open it, why not?

Hi,

where can I find the Main menu block after upgrading from Moodle 1.9 to Moodle 2 (2.2->2.5), the activities of the main menue are in the navigation block, but I cann't delete or move them.

The main menu block is gone, but in the plugins list (website-adminblock) it is shown as active and not hidden.

In the 'Add a Block'-menue it's gone too.

I would like to move the activities and look at the main menue block again, but how?

Regards,

Monica