The European Commission has contacted unspecified hardware manufacturers about Microsoft's licensing policy because it suspects anticompetitive behaviour.
The commission, which described the move as a preliminary fact-finding stage, said it is acting in response to companies which have expressed concern about certain licensing conditions Microsoft attaches to its Windows operating system.
These so-called "nonassert obligations" prevent hardware manufacturers from enforcing any hardware patents they have that may have implications for software.
If, for example, IBM patented a method for speeding up the operations of a computer, the company would not be able to prevent Microsoft or any other competing hardware manufacturer from using the technology.
Hardware manufacturers, such as IBM, Dell, Hitachi and Toshiba, have signed these nonassert clauses because they cannot afford to offer computers without Windows, said Thomas Vinje, a critic of Microsoft and a partner in the Brussels office of law firm Morrison & Foerster.
The commission sent a series of letters to equipment manufacturers requesting information on the agreements they have entered into with Microsoft. So far it has not reached any conclusions, nor has it contacted Microsoft about the issue.
Microsoft was not available for comment.
Vinje claimed that Microsoft started inserting the nonassert obligations into contracts with hardware manufacturers four or five years ago.
The inquiry is separate from an antitrust lawsuit conducted by the commission. The antitrust case focuses on Microsoft's policy of bundling its audio-video Media Player software into successive versions of Windows.
The inquiry into Microsoft Windows licensing agreements with hardware manufacturers could form the basis of a separate antitrust investigation if the commission suspects that the company is using the nonassert clause to stifle innovation among hardware manufacturers.
When a hardware manufacturer "signs a clause like this, it's a pretty big disincentive to innovate", Vinje said.
Vinje's clients include PC manufacturers Dell and Fujitsu.
Paul Meller writes for IDG News Service