Consider your desktop a temporary landing area for files you download. If it is an installation file for a neat new software you are wanting to try, DELETE the installation file once you have your software installed. You don't need it any more. In fact, there really is no reason to save installation files. Chances are, if you ever need to install it again, that file you downloaded (Lord knows when) is outdated, and it makes more sense to just get a fresh one.
If you are downloading books for your Kindle, then drag the book file to the Documents folder on your Kindle, you don't need that originally downloaded file on your Desktop any more. Delete it. Or if you want to save it in a special folder for future use, or sharing, create a special folder to keep in your Documents folder on your main computer (not your Kindle). After you download a book file to your Desktop, decide what you want to do with it. Drag it to your Kindle documents folder, then drag it to your special folder so you know where it is, and keep your Desktop nice and tidy.
Decide what you are going to do with the files you download immediately. Do not let them languish on your Desktop longer than absolutely necessary, or you could end up forgetting them. You wouldn't want to end up with a mess of a Desktop... really unfun to look at or clean up.
