Microsoft CEO Steve Ballmer holds the new Surface as it is unveiled in Los Angeles, California, in this June 18, 2012 file photograph. (Reuters/DAVID MCNEW/Files)

Microsoft Corp Chief Executive Steve Ballmer got a lower bonus than last year's, partly for flat sales of Windows and his failure to ensure that the company provided a choice of browser to some European customers.

Ballmer, who took over as CEO from co-founder Bill Gates in 2000, earned a bonus of $620,000 for Microsoft's 2012 fiscal year, which ended in June, down 9 percent from the year before, according to documents filed Tuesday with the U.S. Securities and Exchange Commission.

His salary -- low by U.S. corporate standards -- remained essentially flat at $685,000.

It is the third year in a row that Ballmer has not earned his maximum bonus, set at twice his salary.

Microsoft's recent financial year was scarred by a massive $6.2 billion write-down for a failed acquisition and lower profit from its flagship Windows system as computer sales stood still

In the company's filing, Microsoft's compensation committee said it took into account a 3 percent decline in Windows sales over the year, as well as "the Windows division failure to provide a browser choice screen on certain Windows PCs in Europe as required by its 2009 commitment with the European Commission."

The company's failure to provide a browser choice in Europe was an embarrassing setback for the software maker, which has been embroiled in disputes with European regulators for more than a decade and paid more than $1 billion in fines for including its own Internet Explorer browser on Windows. It now faces further fines from a new investigation.