Despite telling the world that Windows 7 isn't even close to completion and insisting Vista will be around for a while, Microsoft has released a build of its next operating system to US law enforcement, a court document claims.

Microsoft confirmed the authenticity of a court filing on Wednesday that claimed it has provided a test version of Windows 7 to the technical committee (TC) which is ensuring the company's compliance with its US antitrust settlement.

Microsoft's next operating system is mentioned deep within the document and only states that a build has been made available to regulators.

Tests galore for Microsoft's latest OS

"In addition, the (technical committee) has begun to review Windows 7 itself," Microsoft and regulators said in the filing. "Microsoft recently supplied the TC with a build of Windows 7, and is discussing TC testing going forward. The TC will conduct middleware-related tests on future builds of Windows 7."

So far, neither Microsoft nor the technical committee have commented on the complexity of the tests or what the regulators are looking for. But given the history between the two groups, the software giant will be being watched very closely.