Tougher antitrust enforcement by European Commission regulators could mean trouble ahead for Microsoft, experts warn. Last week's appeals court ruling lifted from Microsoft the immediate threat of a breakup. But, in the coming months, Microsoft will face a tough battle in Europe, experts said. Two cases are pending there, relating to allegations Microsoft's desktop operating systems gave the company unfair advantage in the server market. The EU's decision to block the proposed $43 billion merger of General Electric and Honeywell on Tuesday due to antitrust concerns is a sign of renewed vigor on the part of regulators, said Peter Alexiadis, an antitrust attorney with Squire, Sanders and Dempsey in Brussels. "This is generally a time when the Europeans will flex their antitrust muscle," said Alexiadis. "A lot of it is certain paranoia that the onset of the Bush administration essentially means the death of effective antitrust enforcement.