According To the link above, which is the official windows phone blog, Wp7 will feature custom ringtones in the next big update code named ‘Mango’, although there are a few expected rules here:
To qualify as a ringtone, a sound file must be:
- 39 seconds or shorter
- smaller than 1 megabyte (MB)
- saved in MP3 or WMA format
- not copy-protected (i.e. DRM free)
In short, custom ringtones can be installed using the Zune software on your PC. Once you’ve created an audio file that meets the ringtone requirements, find it in your Zune music collection, right-click the file, and change the Genre field to Ringtone. Then just sync the file to your phone like you would any music track.