Intel Macs are "unlikely" to be able to run Windows Vista, Apple confirmed last night.

Speaking at a packed final session at the Intel Developer Conference(IDF), Apple's senior software architect Cameron Esfahani explained that the two different operating systems - Mac OS X and Vista - have two different ways of starting up.

Speculation had favoured the notion that both Mac and Windows systems would use Extensible Firmware Interface (EFI) software when they launch. This isn't the case, said Esfahani, as only 64-bit versions of Vista use EFI.

"Extensible Firmware Interface (EFI) is the modern and flexible successor to the 20-year-old PC BIOS. It is responsible for initialising hardware in the PC, and importantly, device drivers are stored in the EFI flash memory rather than being loaded by the operating system," said Dan Warne in APC Mag.

"That's terrible news for Intel Mac users who have been hoping that they could dual-boot Windows and Mac OS X on their new Macs: not only are their processors not 64-bit (and thus will never be supported by Windows EFI booting) but Windows Vista won't boot on EFI anyway," Warne added.

Esfahani confirmed that Apple only offers limited support for EFI within Mac OS X and has not included code for older devices and hardware. reports he said: "Windows is a legacy OS. We don't have legacy support." His remark drew applause and laughter from the audience.

However, a recent note from Needham & Co analyst Charles Wolf pointed out that if Apple makes its Intel Macs capable of running Windows, the company could see its market share rise to over 9 per cent - as such a move would be the final argument tempted Windows-switchers would need to move to Mac.

With EFI's use as a system to support legacy devices, Windows users should perhaps heed a Microsoft statement on EFI. The company told developers at IDF that Vista wouldn't have EFI support on launch.

It may be unnecessary to boot a Mac in Vista in order to run Windows applications. Transitive, the company behind Rosetta, Apple's binary code translatior, could theoretically translate from a Windows application to a Mac OS X application. As yet the company has no plans to do so, but its enhanced relationship with Intel could hint at such a move, suggests Hexus.