Brussels' competition commissioner has opened a fresh investigation into Microsoft's practice of using its Windows operating system to push people into using its Internet Explorer browser, following allegations of non-compliance with an EC settlement deal the software giant agreed to in late 2009.

Microsoft, under the legally-binding agreement, was supposed to display a choice screen to its European Windows customers allowing them to pick between IE, Firefox, Chrome and other browsers on the market until 2014.

However, since February 2011 when Microsoft issued a first service pack for its Windows 7 operating system the choice screen had vanished, European Competition Commissioner Joaquin Almunia said in a statement on Tuesday.

Microsoft immediately confessed to what it described as a "technical error" that had removed the choice screen from its OS. It further claimed not to have noticed the choice screen's disappearance, and to have only become aware of the situation when contacted by Brussels officials recently.

As of December last year, Microsoft was claiming to the EC's antitrust commissioner that the choice screen was still available.

Almunia said "we have received indications from third parties that Microsoft has not complied with its commitments in the period from February 2011 until today."

He said that around 28 million new Microsoft customers were probably not shown the choice screen.

We are now opening formal proceedings against the company. If following our investigation, this breach is confirmed – and Microsoft seems to acknowledge the facts here – this could have severe consequences. Needless to say, we take compliance with our decision very seriously. If the infringement is confirmed, there will be sanctions.

Almunia added that he was considering strengthening the monitoring of companies that have signed a legally-binding deal with the commission.

Microsoft, meanwhile, issued a lengthy statement to The Register in which it admitted to having "fallen short" of the company's responsibility to comply with the EC's settlement deal.

It said:

Due to a technical error, we missed delivering the BCS [browser choice screen] software to PCs that came with the service pack 1 update to Windows 7. The BCS software has been delivered as it should have been to PCs running the original version of Windows 7, as well as the relevant versions of Windows XP and Windows Vista. However, while we believed when we filed our most recent compliance report in December 2011 that we were distributing the BCS software to all relevant PCs as required, we learned recently that we’ve missed serving the BCS software to the roughly 28 million PCs running Windows 7 SP1. While we have taken immediate steps to remedy this problem, we deeply regret that this error occurred and we apologise for it. The Commission recently told us that it had received reports that the BCS was not being displayed on some PCs. Upon investigating the matter, we learned of the error.

Microsoft said it had distributed the necessary BCS software to machines running its Windows OS earlier this month and added that it expected to "substantially complete distribution of the BCS software to the PCs we initially missed by the end of the week."

Additionally, the company is conducting an "outside investigation" of the apparent cockup by getting external counsel to conduct a formal probe of what went wrong.

Redmond has also offered to extend its compliance period by 15 months to make up for the prolonged disappearance of the browser choice screen.

"We understand that the Commission will review this matter and determine whether this is an appropriate step for Microsoft to take. We understand that the Commission may decide to impose other sanctions," the company said.

Microsoft further snivelled:

The BCS provides an easy way for users to choose any browser. As agreed with the Commission in 2009, Microsoft uses our Windows Update service to send the BCS software to Windows-based PCs. Once installed, the BCS software checks to see if Internet Explorer is the default browser and, if it is, the BCS is displayed to the user. The Windows Update system uses 'detection logic' to determine which software updates (such as the BCS) to distribute to which PCs. The detection logic for the BCS software was accurate when we began to distribute it in early 2010, and the BCS software was delivered as it should have been. Unfortunately, the engineering team responsible for maintenance of this code did not realise that it needed to update the detection logic for the BCS software when Windows 7 SP1 was released last year. As a result of this error, new PCs with Windows 7 SP1 did not receive the BCS software as they should have. Since most computer users run earlier versions of Windows, we estimate that the BCS software was properly distributed to about 90 per cent of the PCs that should have received it. We recognise, however, that our obligation was to distribute the BCS to every PC that should have received it. Therefore, we have moved as quickly as we can to address the error and to provide a full accounting of it to the Commission.

The timing of the Brussels intervention is interesting given that Microsoft's IE browser is no longer the dominant force it once was in Europe. But the fact remains that, regardless of market share, MS agreed - and then failed - to comply with the competition commissioner's settlement agreement until 2014. ®