You can add custom ringtones and notification sounds easily. There is only one problem with the X10, when you use a mp3 files as your ringtone or notification MediaScape will read it. Really stupid and annoying, then I found out a quick fix for that.
So get a copy of your file, lets say its called song.mp3.
Drag it to your desktop
Then select it and right click and select rename
Now highlight song.mp3 and rename it as song.midi
This will change the file extension as a midi instead of a mp3, MediaScape won't read it.
Now mount your X10 to you PC
Navigate to SD CARD/Media/Audio
In the audio folder there should be 3 folders Alarms, Notifications, and Ringtones. If not just make them.
Now just drag and drop your files.
Easy. Just remember to unmount or you won't be able to see your files, took me a while for me to get that part lol.
-Renaming as .midi didn't affect my songs and the quality was still the same
-If you want back to mp3 just drag to your desktop and rename the song.midi to song.mp3
-If you can't see the file extension open a folder and go to tools/folder options. Then go to View and make sure that Hide extentions for known file types is not selected.