Microsoft has lost its appeal against a record $690m fine imposed by the European Commission.
The European Court of First Instance upheld the ruling that Microsoft had abused its dominant market position.
A probe concluded in 2004 that Microsoft was guilty of freezing out rivals in server software and products such as media players.
There are about a billion PCs in the tech ecosystem and more than 80% of them run Microsoft operating system.
First, is Microsoft a monopoly?
Second, if you think that it is, what should be done about it?
Thirdly, what are your thoughts on the fine imposed?
Finally, what are your thoughts on this:
"A market level of much less than 95 percent would be a way of measuring success," European Competition Commissioner Neelie Kroes told a news conference, referring to the market share of Microsoft's Windows operating system.
"You can't draw a line and say exactly 50 (percent) is correct, but a significant drop in market share is what we would like to see," she said.