Hack Allows Any File Size And Format For Ringtone And Alert Sounds On WP7
By default, ringtone, alert and alarm sounds on Windows Phone 7 have to be under 40 seconds, smaller than of 1MB and can only be in either MP3 or WMA format – there are lots of limitations. However, forum member arses has found a way to circumvent these limitations. As for file formats, he has successfully tested .aac , .amr , .m4a , .ac3 , .aiff , .flac , .mka , .mp2 and .ogg.
If you think this is useful – as noted by WPCentral, you can’t dismiss alerts while the sound is playing, possibly forcing you to wait over 40 seconds – and have write access to the \Windows folder on your phone (usually achieved through the WP7 root tools), head over to the forum thread for instructions.