Ive been what struggling with this for a while, and I believe I have figured out the problem. Because the sound when it starts up is an SD card notification, the SD card isnt mounted yet. This means that any notifications on your SD card cant play, so it uses the standard ring instead of any notifications saved on your SD card. So to fix this, you would want to move the personalized notification from /sdcard/whatever to /system/media/audio/notifications, making it accessible to the phone before the SD card is mounted. However, the phone's memory is write only; you need to be root to do this. I don't want to bother with rooting my phone, so Im sticking with one of the built-in notifications (anything that came with the phone should work).