Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Alas no Mac.....just a PC I'm ashamed to say :(

I have a pc it sucks but there is a way to do it for free in itunes its really simple and once you know what your doing it can be done in less than i min...

find the song you want as a ringtone in your itunes...
find the part of the song you want to use...
right click>get info>options select the start and stop times(the time code of the part of the song you want i usually add a second to the start and stop to make sure i get it all you can also add .01-.99 if you want) click ok
right click the song again>convert to AAC
after it converts listen to it and make sure it sounds right.
then left click the AAC song and press delete>then keep file
then go to your itunes folder>music find the song you just deleted
(this part is important make sure you can see file extensions!!!!!!! if you dont know how its in folder options>uncheck hide file extensions for known file types.)
then rename the extension from .m4a to .m4r (it will tell you it might damage the file or something like that and ask if you want to proceed the answer to that is YES)
then double click it and it goes back into itunes under ringtones section
after that just sync it to your iphone it will be under sounds settings
and the quality is just like it was on your ipod


hope that helps and good luck with it. i know it sounds like a lot of stuff to do but its a really fast process once you do it once. and the best part its all the songs you like and the parts of the songs you like. and also its free
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.