Microsoft is asking users testing its new Windows 7 release candidate to return to their old operating systems.

In a posting to the Engineering Windows 7 blog on Tuesday, Microsoft developers said that users testing the new build of Windows 7 would be asked to revert to Windows Vista rather than the beta releases which testers are currently running.

The reasoning behind the move is that nearly everyone who buys and installs Windows 7 will be doing so from a Vista machine, rather than a beta release of Windows 7. In order to obtain correct feedback, testers will be asked to install the release candidate from Vista.

"We're just trying to be deterministic and engineer the product for the real world," the developers explained.

"As an extended member of the development team and a participant in the beta programme that has helped us so much, we want to ask that you experience real-world setup and provide us real-world telemetry."

The developers noted that they will include an option for testers who do not wish to revert their systems.

Microsoft's request to testers comes before a release candidate build that some believe will be just weeks away. Last month an accidental posting by Microsoft dated the release candidate build as May 2009.

The final commercial versions of the new Windows operating system are expected to be released as early as November of this year.