The startup sound for my Q9c from Sprint is annoying, especially when it occurs after a late night automated backup. While the startup sound respects the volume and silent modes, turning the phone to silent every night and remembering to reset it in the morning is silly. The steps needed are:
WARNING: Please have a backup handy before mucking with the registry.
The solution is to edit the register (I use Resco Explorer):
\HKEY_LOCAL_MACHINE \system \Startup \1 dll = *none*
Note: The original value on my phone was \windows\AnimEngine.dll.
PS: Alerts by Omnisoft can do many tasks based on time and events, but that seemed overkill for this function.