The European Union says some 100 million people using Microsoft Corp. software will be asked to choose between rival Web browsers by mid-May under a deal it struck with the company to settle antitrust action.

Microsoft has started this month sending updates to Windows computers in Europe so that when computer users log on, they will see a pop-up screen asking them to pick one or more of 12 Web browsers to download and install.

The EU dropped its last pending antitrust case against Microsoft after the company offered alternative browsers to the one it distributes with the Windows operating system. Rivals say that was an unfair way of putting Internet Explorer on most of the world's computers.