Microsoft has apologised after the European Commission opened a investigation over its failure to provide customers a web browser choice, saying it was a mistake.
"While we have taken immediate steps to remedy this problem, we deeply regret that this error occurred and we apologise for it," the company said in a statement on Tuesday.
To ease EU competition concerns in 2009, Microsoft promised to provide Windows users in Europe a "choice screen" enabling them to choose a web browser instead of Microsoft's default Internet Explorer.
"We have fallen short in our responsibility to do this," Microsoft said.
The European Commission warned that Microsoft could face a fine if an infringement were discovered.
Microsoft said that due to a "technical error," it failed to deliver the "browser screen choice" software to PCs with a service pack 1 update to the Windows 7 operating system.
The company said it developed software to fix the problem on July 2, one business day after it discovered the problem.
The statement said distribution of the BCS software was expected to be substantially complete by the end of the week.