30 Mar 2009, 11:59
Go to admin -> setting -> thumbnails.thumbnail.boxwidth and boxheight. You can set the maximum width and height of the thumbnails. Also see resizetype to select if you want thumbnails to crop within that box size, or if you want them to constrain within that box size.
Now, go to manage one of your folders, and click "recreate thumbnails in this folder", and thumbnails will be created. Now, you can go back to the settings, and change the thumbnails creation properties, and then go to manage a new folder and create thumbnails again.