Word of warning: Vista OS X '09
For those of you supporting laptops that aren't locked down (in our case, laptops owned by the students, primarily sixth form), a word of warning about this little gem:
Vista OS X
This is supposed to re-skin Vista to look like OS X. We've had two muppets - sorry, I mean Apple fanboys - in the last month install this and have it trash their Vista installation. The primary symptom is that the machine will boot, but never display the Vista welcome screen - all you will see is the mouse pointer on a black background. Safe Mode and Last Known Good Configuration also exhibit the same problem.
Having looked through the site it's clear that it replaces several core files to do with the theme subsystem in order to achieve the skinning effect. My guess is that the installer isn't very reliable and manages to miss one of them.
There is a page for uninstall problems, but the student I saw this morning informed me he'd tried these steps, and it actually made the problem worse.
I found that booting from a Vista install DVD, selecting Repair, and using System Restore to go back to a checkpoint before the install fixed it. Huzzah for System Restore, etc.