Leopard has a cool new feature called Live Preview, which displays a thumbnail image of a file's contents as the file's icon. Live Preview lets you quickly see what a file holds, whether it's a Microsoft Word doc, a PDF, an image, or some other type of data. That sounds like a great idea, and it is, unless your desktop is littered with files. In that case, your Mac may behave erratically during the startup process, as it tries frantically to display thumbnails of the contents of all the files scattered across your desktop. Not that I personally have ever experienced this problem, but you may want to try to avoid it.
During the boot process, Leopard will look through each and every file on the desktop, in order to build its associated thumbnail icon. If there are too many files, your Mac may short out (figuratively speaking), slowing down the startup process, and leaving you staring at a beach ball icon for a painfully long period of time.
You can nip this problem in the bud by organizing your computer (or at least your desktop), and moving desktop files into appropriate folders. Start with the default folder set that each user account inherits when you create it (Documents, Downloads, Movies, Music, Pictures), and add other folder categories as necessary. The goal is to pare the desktop down to no more than a few files that you're actively working on.
