A two day appeal hearing has ended into the European Union's landmark antitrust ruling against Microsoft.
Microsoft's software outsells its competitors nine to one
The computer giant has been attempting to get the anti-competition ruling from the European Commission suspended.
Back in March, the Commission, the EU's executive, also told Microsoft to share technological secrets with its rivals.
The court president Bo Vesterdorf has said he will rule on a possible suspension of the measures "as soon as possible".
'Level playing field'
Microsoft argues that one of the key demands, that the company strip its digital media software from some versions of the Windows operating system, would
do the most damage to small companies and their customers.
The Seattle-based firm is also asking for the suspension of an accompanying 497m euro ($613m; £340m) fine.
Commission lawyer Per Hellstrom argued making
Microsoft sell a version of Windows without its own
Media Player would "level the playing field".
It would increase the possibility of rivals such as Real Networks' RealPlayer being used.
But Mr Vesterdorf, president of the European Court
of First Instance, challenged representatives from the European Commission what the outcome of such an order would be.
The European Commission's argument is that Microsoft has abused its dominant market position.
To rectify this, it ruled that Microsoft should give rivals details of its Windows software systems, so that they can more easily develop products that will work easily on Microsoft-installed computers.
It also wants Microsoft to remove its Windows Media Player so that rival products s
Microsoft has countered that both parts of the ruling would do it irretrievable harm.
Linda Averett of Microsoft told the court in Luxembourg on Friday that many websites and software products would not work without the Windows Media Player.
She said that without the player, customers who buy computers with Windows "are very likely to feel deceived when they find that websites don't work".
"This is a serious problem," added Ms Averett.
Real Networks gave the court a demonstration of its rival product on a computer which had the Windows Media Player removed.
The company claimed that it was possible to enjoy music and video clips on a "stripped-down" version of Windows without causing the system to malfunction.
The decision of the Court of First Instance on Microsoft's suspension appeal is expected in four to six weeks.
Whatever its verdict, Microsoft is set to continue with its legal challenge to have the Commission's ruling permanently overturned, a process which is expected to take a number of years.