I had noticed that when you boot from a Mac OS X DVD and launch the Terminal, the open command is not available, so you can't launch GUI apps. It just occurred to me that just because the open command isn't on the CD doesn't mean you can't run it - it's on your hard drive! So you can type something like this:

/Volumes/Macintosh\ HD/usr/bin/open \
/Volumes/Macintosh\ HD/Applications/TextEdit.app

...to launch TextEdit. Unfortunately it doesn't work with more complicated applications, and most notably doesn't work with the Finder, but it might come in handy.

As I previously noted, you can do the same thing with Windows Vista, except that you can launch applications directly without using an open command.