Microsoft has lost its appeal against a £343 million fine in the European Court of First Instance and, as an extra blow, will have to pay 80% of the case's legal costs.

The record fine, imposed by the European Commission, related to an investigation back in 2004 that found Microsoft guilty of blocking competitors from offering rival software solutions, especially in regards to Media Player.

The European Court of First Instance upheld the ruling, and the subsequent fine, and a court statement said: "The Court of First Instance essentially upholds the Commission's decision finding that Microsoft abused its dominant position".

One part of the ruling, to do with an independent monitoring trustee was changed and Microsoft has two months to file another appeal to a higher court.

Michael Reynolds, of law firm Allen & Overy, commenting on the ruling said, "It provides legal certainty now as to what you can and you can't do in relation to information you have to make available to companies who compete in your environment to enable them to be a viable competitor".