Apple posted a new version of its Boot Camp software on Wednesday. Version 1.2 now supports 32-bit Vista.
The update also includes updated drivers including trackpad, AppleTime, (synch),
audio, graphics, modem and iSight camera.
Installation of Vista requires a full version of Vista, not an upgrade:
Vista Home Basic, Home Premium, Business, or Ultimate and at least Mac OS X 10.4.6.
The full system requirements, a list of changes in version 1.2, and information on how to upgrade to this version are on the Apple Boot Camp page.