Download the zip file with the code; open the solution in VS 08; SpeechLib is missing.
We run into this in our WinForms project at work when some devs are on Vista and some are on XP.
Here's what's wrong: SpeechLib is a built-in COM component. You added it in Vista (version 5.3). I'm using it in WinXP (Version 5.0).
There is no good way to get around this that we've found. If MSBuild could report the OS version number without a custom target you can conditionally load each one depending on OS.
To fix (if you're on XP): delete SpeechLib reference. Click Add Reference... Select COM tab. Scroll down to Microsoft Speech Object Library.