Ugh, one of my huge pet peeves with phones. They should **never** make noise on startup. It's happened to me - your phone spontaneously restarts, it makes that stupid noise.
If you silence the phone before you power off, it should not make a noise on startup. That's the only way that I know of for Droid phones without a permanent root on the phone.
I am trying this in Tasker, but I have a problem. I set up the profile and tasks to boot up in silent but it doesnt work and my profiles and tasks are gone. not sure what is going on, I have Tasker enabled