The consortium alleged that Microsoft has been illegally bundling software into its XP operating system to stifle demand for rival products and unfairly using its Windows monopoly to give it a foothold in new software markets.
The case has been brought by industry body the Computer and Communications Industry Association, which also claimed Microsoft's Office desktop productivity suite is designed to hamper interoperability with other software, such as Linux.
Ed Black, chief executive at the CCIA, accused Microsoft of "myriad anti-competitive abuses".
The CCIA lodged the complaint with the European Commission on 31 January, accusing Microsoft of violating the EU Treaty's Article 82, which governs antitrust matters.
Central to the case is the battle for control of the lucrative web services market. However, in a move that will further anger the CCIA, Microsoft has applied for a wide-ranging patent that will cover a variety of functions related to its .net initiative, including the application programming interfaces that control links to other systems.