Vista won't boot on current x86 Macs
Today, Microsoft development manager Andrew Ritz announced that support for the new Extensible Firmware Interface (EFI) won't show up in Windows Vista until next year, after the release of Longhorn Server. EFI support will only be added to the 64-bit versions of Vista, so 32-bit systems with EFI won't be able to boot the new OS.
EFI is Intel's BIOS replacement for future PCs, and it's already being used in Apple's x86-based Macs. However, those machines use Core Solo and Core Duo processors, which are still 32-bit. With no 32-bit EFI support in Vista, only Macs with Intel's upcoming 64-bit Conroe and Merom chips will have a shot at booting Vista, and then only some time after its initial release. Current x86-based Macs may have to rely on emulators and compatibility layers, such as Virtual PC or Darwine, to run Windows applications.