Outlook 2010 folder view - Folders Arrangment

One of my users has logged on to find the arrangement of the folders in outlook has changed, not how the mail is sorted in outlook but the folders themselves. Normally 'Calendar' is at the top but its now half way down the list and I;m not entirely sure how to move it back. How do you sort out the arrangement of folders in folder view?

I have included a very basic screenshot to show you what I mean.
folders.jpg