If your mailstore is getting full and you need to find what is taking up so much room, Outlook 2007 makes it easy. Just do the following . . .
1. Go to your Inbox (or Calendar).
2. In the Search Inbox (or Search Calendar) text box, type size:> and then the minimum number for the size (example size:>1000000 which would be 1MB).
Now you can examine the items and delete or move them as you see fit.