Microsoft on Thursday made a sweeping attempt to put its long-running regulatory problems behind it as it unveiled what it claimed was a broad new level of transparency and openness for its Windows operating system and other big-selling software.

However, the gambit drew a lukewarm response from the European Commission, which expressed scepticism about the sincerity of the group’s intentions. It also pointed out that separate allegations that Microsoft had illegally “tied” the Internet Explorer browser to its Windows operating system, which form part of an ongoing probe, had not even been addressed.