[Typo3] Clean up unused data in database

[Dirk]

>> Now my question is , is there a way to let typo3 clean up the database, but 
>> only clean up unused elements...without having to go into php/myadmin and 
>> clean every table manually...?
>
>Look in the extension repository. I remember KJ Recycler but there are a
>number of such extensions.

"KJ Recycler 2005" doesn't look into (at least) sys_todos and sys_todos_users_mm. The alternatives "Clean Database" and it's sibling "MK Wastebasket" however do show deleted elements in those tables (they're correct, there are some).
Does anybody know if there's a reason for hiding sys_todo*?

TIA,
Dirk

Another question: how to get rid of tables created by extensions that are no longer active?