Just a note that for those (presumeably few) people who are running the Mac Print utilty Bonjour will currently be unable to install SilverStripe via the Windows-based Installer.
In the mean time, the "fix" appears to be to uninstall Bonjour.
The bug is with httpd/php rather than anything to do with SilverStripe per se.
This is not a problem if you use the .tar.gz download, having got a webserver running on your computer (nor does it relate to running this on a Mac, as obviously you're not using the Windows installer!)
The bug will pop up the following Windows error message:
php-cgi.exe - Unable to Locate Component
The application has failed to start because dnssd.dll was not found. Re-installing the application may fix this problem.
We expect that this is an edge case (few Windows users will be installing SilverStripe and Bonjour?); but DO reply if this a problem for you so that we can investigate solving it; post your windows, silverstripe and bonjour version numbers...