Thanks guys
I think I may have found the answer: MacPilot 2.3.5 claims it can disable the startup chime (scroll down). Haven't tried it yet though
Steve
"About Mac Pilot
Scared of the terminal or can’t be bothered to remember those commands to customize your system the way you want? Mac Pilot is your digital savior. Easily enable and disable hidden features in Mac OS X, optimize and repair your system, and perform numerous routine maintenance operations with the click of a button!
Pro user or not, you can now increase computer performance with only a few clicks of the mouse. Optimize your network for broadband connectivity, completely customize Apple File Sharing, perform essential maintenance without having to remember mind boggling acronyms, and much more. However, those are just a few of the many reasons why Mac Pilot is your choice over Cocktail, TinkerTool, and Onyx!
Enable the “cut” option in the Finder, disable menu items for security, disable icon caches, set history limits, erase recently used files, prevent your dock from being modified, turn off all system animations, increase the speed at which windows resize, change which format screenshots are taken in, set a default name and location for screenshots, disable a secondary processor, disable the startup chime, and even change the log-in window picture!
We welcome you to put Mac Pilot to the test against our competitors. Features, stability and interface say it all — but why don’t you be the judge? Download your free 15-day limitless evaluation now."
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http://www.apple.com/downloads/macosx/systemdiskutilities/macpilot.html