As Microsoft prepares for the consumer launch of Vista, rivals slammed the software, saying it breaks the same European antitrust laws that Windows XP abused in 2004, and that it will be riddled with bugs.

"Microsoft has chosen to ignore the fundamental principles of the Commission’s March 2004 decision," said Simon Awde, chairman of the European Committee for Interoperable Systems (ECIS) in a statement on Friday, adding that the new product goes even further, by leveraging its desktop dominance to compete on the internet.

ECIS filed a formal complaint about Vista to the European Commission's antitrust division a year ago. The Commission said at the time that it would examine the complaint carefully. That examination is understood to be still ongoing, however Commission spokesman Jonathan Todd wasn't immediately available to comment.

On Friday the ECIS described Vista as "the first step in Microsoft's strategy to extend its market dominance to the internet." Microsoft’s XAML markup language inside Vista was designed to replace HTML (Hypertext Markup Language), an industry standard used for publishing material online, it claimed.

XAML is designed to be dependent on Windows, and therefore not interoperable with other systems, ECIS said.

In addition, Vista and Microsoft Office 2007 will introduce the Open XML file format called OOXML in a move to replace the ODF industry standard.

"Unlike the ODF file format which operates on multiple vendor platforms, Microsoft's OOXML today only runs seamlessly on the Microsoft Office platform," ECIS said.

"With XAML and OOXML Microsoft seeks to impose its own Windows-dependent standards and displace existing open cross-platform standards which has wide industry acceptance, permit open competition and promote competition-driven innovation," said Thomas Vinje, a partner at law firm Clifford Chance and legal advisor to ECIS.

"The end result will be the continued absence of any real consumer choice, years of waiting for Microsoft to improve — or even debug — its monopoly products, and of course, high prices," he added.

Microsoft declined to comment on the ECIS statement. With Vista and Office 2007 scheduled to debut in retail stores on Tuesday, the company is gearing up for a marketing blitz, which in Belgium will include the lighting up of the Atomium — a construction modeled on the structure of an iron molecule that dominates the northeast skyline of the city.

Vista and Office 2007 were available to business users in the fourth quarter last year.