This is kind of a strange story, but why the hell can't he get it running? This is when to call in VMWare and have a nice set of clean machines available. Apparently he was running SlimServer, which sounds slightly immoral so I am sure he deserved the non-functioning environment. Anyway, nice thing about XP is early cancellation, but, he could have just asked for help...
That said- development environment set up is not that easy. I had one J2EE project where we had a two day process. For my last Rails project, it was a about two pages on the wiki, most of it related to SQL Server driver (don't ask) and Ferret. It did remind me to not depend on the availability of external resources for the install procedures though- what's out there on the Rails Gem servers can change.
What's killing everyone on one of my internal corporate projects is svn+ssh. That said, our most recent hire nailed it pretty well, even though it was his first time using a Mac and NetBeans, and I am using RadRails on Windows.
Anyway- it's worth writing up the procedures for the development environment set up, and then having the new person update those when they come on board as their first task. Of course, if no one has started for a while, chances are the instructions just won't work.