Earlier this week Microsoft had planned to reverse an earlier decision, and allow low-end Vista owners to use the operating system under virtualisation on the Mac platform - but the company switched again and banned virtualisation before the announcement could be made.

"Microsoft has reassessed the Windows virtualisation policy and decided that we will maintain the original policy announced last Fall," a Microsoft spokesperson said in a statement provided to Macworld.

However, Microsoft's position earlier this week was decidedly different. In a meeting with Macworld the company said that due to customer feedback on virtualisation, they would be changing the EULA (End User Licensing Agreement) to allow virtualisation of the Vista Home and Home Premium.

"We are always listening to the community with regards to licensing," Scott Woodgate, director of the Windows Vista team, told Macworld. "Security is still a concern, but we are enabling the customer to make that choice."

Since Microsoft will not allow Vista Home to be run under virtualisation, users are back where they started - running Vista Business, Ultimate or Enterprise in order to comply with the licensing agreement.

Virtualisation specialist Parallels had welcomed the decision to allow virtualisation across the Vista product line and said they will continue to work with Microsoft on virtualisation.

"We were obviously disappointed," said Ben Rudolph, Parallels director of corporate communications. "Any annoucement from any OS vendor that makes it easier to use their technology with virtualisation is a welcome one."

Rudolph said that most Parallels users are running their virtual machines with Windows XP, not Vista at this point.

"Of course, the decision to license or not license Vista for use in a virtual machine is up to Microsoft, and we will certainly respect their decision, but we will continue to advocate on behalf of our users and we'll continue to work with Microsoft on the issue," said Rudolph.