Although the Samsung i8910 is arguably the 'best' S60 phone currently available, it doesn't come without its faults. One of these faults is what seems to be an issue that has been overlooked by Samsung: being able to disable the startup/shutdown sounds. Unlike Nokia's S60 phones, the Samsung i8910 will still make some noises even when warning tones are set to 'off'. This annoyed me, so I started hacking away at the i8910 until I came up with a solution.
What you'll need:
-A hacked Samsung i8910 (refer to THIS post)
-THIS zip file (extract it and copy all files to your phone)
-ActiveFile(already signed with Leftup certificate)
1)Copy the 101F8763.txt file to C:\Private\10202be9
2)Copy the Startup.mp3 and Shutup.mp3 files to E:\Sounds\Simple
3)Restart your phone.
This works beautifully with IG2 firmware. If you have any issues, please leave a comment and I'll get back to you.