An EC spokesman said: "This Statement of Objections supplements one sent to the company a year ago and adds a new dimension to the commission's concerns that Microsoft's actions may harm innovation and restrict choice for consumers.
The spokesman added that Microsoft may have violated European antitrust rules by "using illegal practices to extend its dominant position in the market for personal computer operating systems into the market for low-end server-operating systems".
Microsoft has two months to reply to the latest statement of objections, which the commission said was "now merged with the existing procedure triggered by a Sun Microsystems complaint".
The first case was sparked by a 1998 Sun complaint alleging that Microsoft was using its Windows operating system software to force rivals to withdraw from the market for server software.
It focused on Microsoft's alleged discriminatory licensing and refusal to supply software information to enable rival server products to operate with older versions of Microsoft's Windows operating systems.
In February of last year the commission launched a separate investigation in order to ascertain whether Microsoft was following the same path with the latest version of Windows 2000.
As with the first case, the commission believes that Microsoft may have withheld key interoperability information from vendors of alternative server.
The Commission said it was also investigating allegations that Microsoft was illegally tying its Media Player product with its dominant Windows operating system. "Microsoft may thereby deprive PC manufacturers and final users of a free choice over which products they want to have on their PCs, especially as there are no ready technical means to remove or uninstall the Media Player product," the Commission said.
"Competing products may therefore be at a disadvantage which is not related to their price or quality and the result is a weakening of effective competition in the market, a reduction of consumer choice, and less innovation."