How do I turn off the power-on sound and camera sound in a Galaxy S II? I have followed several guides and can't get any of them to work on my Galaxy S II. How do I disable these sounds?!
This requires a rooted phone. There is a good guide here: http://forum.xda-developers.com/showthread.php?t=1103399

If you don't have ADB, get the full Android SDK from here: http://developer.android.com/sdk/index.html (it might come in useful multiple times, and all app developers should already have it). Don't trust websites offering ADB alone unless it the official Android site. After installing it, browse to the install directory, then "platform-tools", then open the command line -- on Windows 7, this is done by shift-right-click and choose "Open command window here", then type "adb".

Power-on sound

This sound file is NOT in the standard location for Android (/system/media/audio) so most guides haven't worked for me.

Connect your phone to your computer and open ADB. Go into shell with "adb -d shell". Now become super-user with "su" - your phone must be active and unlocked - a dialog will open which you accept. In ADB again: " mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system".

Now rename the sound files so they can't be found!
"cd /system/etc"
"mv PowerOn.wav PowerOn.wav.old"
"mv 1_Power_on.ogg 1_Power_on.ogg.old"

Restart your phone. There should be no power-on sound.

Disable camera sound

Again. this sound file is also not in the standard Android location (/system/media/audio/ui/camera_clicker.ogg) so most guides haven't worked for me.

First, make your / read-write. In ADB, go into shell then type "cat /proc/mounts", find the line where "/" is the second column, and remember the first column which in my case is "rootfs". In ADB do "mount -o rw,remount -t yaffs2 rootfs /"

Now you need to edit the root default.prop (that is, "/default.prop"). In ADB: "cp /default.prop /sdcard/default.prop". Copy it from your SD card to your computer (Samsung Kies is the easier way). Add the line "ro.camera.sound.forced=0" and save. Put the edited file back onto your sdcard with the same name. Now "cat /sdcard/default.prop > /default.prop"

Restart your phone. Open the camera app. Taking photos and videos should now be silent.