Microsoft’s sudden conversion to openness and interoperability last week did not impress the European Commission. Today, the antitrust-enforcing arm of the European Union imposed a $1.35 billion fine (899 million Euros) on Microsoft for failing to comply with a 2004 order to supply interoperability data for its products to its competitors. That brings the total fine to $2.5 billion.

At a press conference EC commissioner Neelie Kroes said of Microsoft’s last-minute overture last week: “We don’t want talk, we want compliance. If you cheat the rules, you will be caught.” She also noted that was Microsoft’s fifth announcement about improving interoperability.

One thing is for sure, if Microsoft does not start acting sincerely in its interoperability efforts, the EC will just keep on zinging it with fines.