Updated from 7:45 a.m. ESTMicrosoft ( MSFT) shares slipped Thursday after its top executives failed to reach a settlement in the software maker's ongoing antitrust proceeding with the European Union and said the company would appeal a negative ruling. The breakdown opens the door to the imposition of marketing restrictions and a fine expected to fall in the hundreds of millions of dollars when European Union Competition Commissioner Mario Monti proposes a final penalty in Brussels next week. Shares of Microsoft were recently down 49 cents, or 1.9%, at $24.65, a fairly subdued reaction. "I guess you could chalk me up as one of those guys that doesn't view it as that big of a deal," said Alex Vallecillo, a senior portfolio manager at National City Investment Management Co., whose funds hold 2.4 million Microsoft shares. "At the end of the day they're probably going to end up paying some money to the EU to resolve this thing once and for all and make some product modifications," he added. But "the scope of what I've heard doesn't worry me." In a draft EU ruling, Microsoft was found culpable of engaging in monopolistic abuses of its dominant position in the software market. Among other things, regulators object to the way it packages video- and music-playing program with its Windows operating system, which runs more than 90% of the world's computers. The EU is expected to propose that Microsoft remove Media Player technology from Windows or require computer manufacturers to install competitive media players with Windows. The ceiling for EU fines is 10% of a company's global sales, which would be north of $3 billion in Microsoft's case, although nothing that large is anticipated.