This file from Curse.com will also get rid of the annoying error sound if you don't want to deal with the scripts.

Error Sounds Be Gone!
http://wow.curse.com/downloads/wow-a...ject-8021.aspx

I use this on my main account with music and all other sounds on, except the one where my toon keeps telling me "I can't cast that yet". Yes, I did get sick of that too. Not sure what all this silences along those lines, as I've played this game alot without sound till I grabbed this. I used to just play with my music player in the background. But you can also grab another addon that's called Move Anything here:

http://wow.curse.com/downloads/wow-a...-anything.aspx

I used this to move that red text from the middle of my screen to the side so I can see the fights better. Keep in mind, it must stay on at all times if you do move anything around. Once turned off, everything will be back to it's original position.