Actually, it wasn’t our IT manager’s call. She knew better, but senior management overruled her, thinking that the security would be better (we do litigation support) with Vista than XP, with all the viruses and hackers out in the world.
Ah! Senior management, who are NOTED for their computer acumen...
I found that people 55 years+ usually have a very hard time getting the hang of computers, and Very Important People that age or older were Too Important to have to deal with such mundane things - so their secretaries or underlings did it for them.
However, the Very Important People usually could be found making major decisions such as the one you described.
Of course, when the stuff hits the fan afterwards, worker bees like your IT manager are the ones who have to work the extra hours and bear the brunt of the ill will...