What's Microsoft's plan for fighting back at the EC when the EC continues to win in court? Threaten with embargos. While it doesn't sound that harsh coming from them, Microsoft is now stating that they may have to delay the release of Vista in the EU further than in other parts of the world because they fear it will make them a target of more antitrust lawsuits or bring other legal friction. They have sent a list of proposals out, and say that a hold back will be dictated by the EC's response:

"Once we receive the Commission's response, we will know whether the Commission is seeking additional product design changes that would result in a delay in Europe," the company said in a statement.
Of course, the EC completely denies that any action they take would leave them responsible for a delay in the release of the software. Some in the EU are upset over this, getting angry at either side. Some lawmakers stated they were upset with the EC's handling:

"It is alarming that one of the world's most successful technology companies considers the European Commission's attitude a risk factor that might delay European companies' access to future Microsoft products such as Windows Vista," four lawmakers wrote in a letter to the commission. "Europe needs to encourage innovation in the technology sector."
Given that MS aims to bring more integration than ever into Vista, the EC could probably easily come up with plenty of ammo to attack them again. Are their concerns legitimate? Or is this is a ploy by Microsoft to try and force the EC's hand?