These solutions work, BUT there is a critical step left out regarding importing your own self made ring tone/sound clip files that didn't orginate from itunes.
If you only change the extension of a file (for example from .mp3 to m4r) itunes will still not recognize the file as a "tone", even if you drop it in the media folder along with the other "tones" even after you shutdown, restart, add file, add folder, etc.
1. You have to first add the file to itunes to convert and change the extension (simple enough, and I mean add it to your library so it is in itunes either by importing, drop it in your library, add file/folder/etc).
2. Next create an *aac version of the file (this will in essence convert whatever format you have to an aac "itunes friendly" format).
3. Once you have the aac version of the file you then can change the extension allowing itunes to differentiate the file and pull it into "tones" (I drag & drop the aac version file onto the desktop and append the extension to .m4r which designates a "tone", but you can probably right click on the aac version and "show in windows" to change the extension right there).
4. Once your file is changed (to .m4r) add it to your library and it should show up in your "tones" library of which you can sync and manipulate as needed.
5. Clean up; I like to go back and delete both the original and the converted tracks to keep it clean.
*to convert to an aac file you have to make sure your import settings in preferences are set this way and not to mp3 for example.
This works, I've done been able to reproduce it numerous times. This kept me up for several nights, and is my first post hoping I may spare some people the same aggravation!