European regulators have stepped up their antitrust investigation against Microsoft.
The Commission published a 'Statement of Objections' on Wednesday, saying the software company had failed to uphold an earlier commitment to offer a choice of browsers to European Windows users.
Microsoft was compelled to begin showing a 'browser choice screen' to European users setting up a new Windows PC following a 2009 settlement with the Commission — a settlement the Commission now feels has been breached.
"The Commission takes the preliminary view that Microsoft has failed to roll out the browser choice screen with its Windows 7 Service Pack 1, which was released in February 2011," the Commission wrote in its statement. "From February 2011 until July 2012, millions of Windows users in the EU may not have seen the choice screen."
Microsoft admitted in July that it had "fallen short" in its responsibility to make a browser choice screen available.
"Due to a technical error, we missed delivering the [Browser Choice Screen] software to PCs that came with the service pack 1 update to Windows 7," Microsoft said at the time.
Now the statement of objections has been published, Microsoft has to reply within one month, or it can request a longer period of around two months by seeking an extension.
"The Commission takes the preliminary view that Microsoft has failed to roll out the browser choice screen with its Windows 7 Service Pack 1" — Commission statement
A statement of objections "must be used in procedures in which the Commission intends to adopt a decision adverse to the interests of the addresees", according to a European Commission document (PDF).
"Precedent tells us that [a Statement of Objections] does not issue unless the Commission believes it can make out its case and if necessary justify the imposition of a prohibition decision," the Initiative for a Competitive Online Marketplace writes (PDF). "The [Statement of Objections] cannot therefore be dismissed as a mere preliminary step, but rather is already the product of considerable investigatory work."
If it is found Microsoft failed to honour the terms of a 2009 EU antitrust ruling, Microsoft could face a fine of up to 10 percent of its annual turnover.
"We take this matter very seriously and moved quickly to address this problem as soon as we became aware of it," a Microsoft spokesperson said in a statement on Wednesday. "Although this was the result of a technical error, we take responsibility for what happened, and we are strengthening our internal procedures to help ensure something like this cannot happen again. We sincerely apologize for this mistake and will continue to cooperate fully with the Commission."