Backing up what DLK said, it depends on your phone. I would try to use Google or try HowardForums, a really good source for cell phone tips/tricks/mods. The question has probably been asked/answered on HowardForums if your phone makes it difficult to upload ringtones. Personally, I have a Samsung on T-Mobile (not for long thanks to the G1!!), which will only play DRM'd MP3s bought through T-Mobile for ringtones. However, there is a loophole in the software that allows you to play a different format - 3gp - with no DRM. I don't recall where I downloaded it from, but I use a program called "Super" to convert the mp3s to the 3gp format. I then use bluetooth to get the 3gp file over to my phone. Not the easiest thing to do in the world, but worth it since I usually do about 5 ringtones at a time.