This is so easy it’s sinful. Of course, you need iTunes and an iPhone for this.
You just change the file extension from .m4a to .m4r. That’s it.
First, grab the .m4a file here. Click “Save” when your computer asks, and remember where it is saved. It will probably be in something like “Downloads.”
Here’s how to change the file extension in Windows Vista.
1. Open any folder in Windows Explorer.
2. Find the “Organize” menu at the upper right.
3. Open “Folder and Search Options”.
4. In the “View” tab, uncheck the box that says “Hide extensions for known file types.”
5. Click “Apply” and then “Okay.”
6. Find the .m4a file that you downloaded. You should see something like “Beethoven’s 5th.m4a”
7. Right click to “Rename” the file. Change the “a” in .m4a to an “r”.
8. Double click the renamed file and it will open in iTunes as a ringtone. Then your iTunes will add it to your iPhone the next time you sync.
Changing the file extension on a Mac is very similar. You just use “Finder” instead of “Windows Explorer.”
I’m going to leave comments enabled on this page so that you can ask for help if you have trouble.