how do u make custom ringtones with windows??
You need some software to edit the MP3/AAC files, to pick out the 30 seconds or less you want to use.
Once you do that, if the file is an AAC (.m4a extension) just rename it to .m4r and drag it back into iTunes.
If it is an MP3 file, put it in iTunes, convert it to AAC, drag the converted AAC file back out of iTunes, rename the extension as described above, then drag it back in.
Files have to be AAC, and they have to have the extension .m4r. And they have to be under 30 seconds.
Other people in this thread have reported that the ringtones have to have a unique name, not the same name as another song in your Library. I have not experienced that; most of my ringtones are named the same as the original files, and they work just fine.