"Top Posters" block in Views

Hi all

I am struggling to create a block using Views to display Top Posters. In two Drupal 7 sites I run, both with the exact same versions of Drupal and Views, one seems to have a Top Posters view built into the defualt list, just requiring enabling and configuring, the other doesn't.

I have looked in vain how to create a Top Posters view using the Add View wizard, trying to emulate what is on the other site, but I can't see the appropriate options to select.

For example, I select User from the menu, then it only gives the option of Newest/Oldest, nothing like these options in the ready made View:

User Stats: Value (Posts)
User Stats: Statistic name (= post_count)

How on earth do you get thes options in to the View?

Thanks in advance for any help!