Users running pirated or counterfeit copies of Windows XP or Windows Server 2003 can now download Internet Explorer 7, Microsoft announced Thursday.

From the moment it released IE7 almost a year ago, Microsoft has restricted the browser to users who can prove they own a legitimate copy of the operating system. Before Microsoft allows the browser to download, it runs the user's PC through a Windows Genuine Advantage (WGA) validation test, a prime part of XP's antipiracy software.

When it instituted the requirement in 2006, Microsoft said rights to IE7 was one of the rewards for being legal. It changed its mind Thursday, saying the move is in users' best interest.

"Because Microsoft takes its commitment to help protect the entire Windows ecosystem seriously, we're updating the IE7 installation experience to make it available as broadly as possible to all Windows users," said Steve Reynolds, an IE program manager in a posting to a Microsoft company blog. "With today's 'Installation and Availability Update,' Internet Explorer 7 installation will no longer require Windows Genuine Advantage validation and will be available to all Windows XP users."

Microsoft has consistently touted IE7 as a more secure browser, and post-launch patch counts back that up. In the past 11 months, IE6 for Windows XP SP2 has been patched for 22 vulnerabilities, 20 of them rated critical. IE7 for XP SP2, however, has been patched only 13 times; 10 of those fixes were ranked critical. In fact, when Microsoft announced that IE7 would not be offered to users running illegal copies of XP, some analysts questioned the company's commitment to security.

This is the first time that Microsoft has removed a WGA check for a major product. Among those that still require validation are Windows Defender, the company's antispyware software, and Windows Media Player 11.

Several people who left comments on Reynold's post wondered if there's more to the decision than meets the eye. "I am guessing that this is in reaction to Firefox's growing market share," said someone identified as Dileepa. "I am not surprised at this at all."

Mozilla Corp.'s Firefox has gained some ground on Internet Explorer since IE7's launch. According to Net Applications, a Web metrics company, Firefox's share is up by about two percentage points since October 2006, while IE's total -- IE6 and IE7 combined -- slipped by more than three points.

IE7's uptake was dramatic late last year, when it went from about a 3 percent share in October to 18 percent in December, but growth has slowed. Since April, for instance, it has increased its share by four percentage points, almost all of it at the expense of the older IE6.

The IE7 update also sports a few tweaks: The menu bar is now visible by default, for example, and a new administration kit that includes a revamped MSI installer is available to smooth corporate deployment.

Users can download IE7 from Microsoft's site immediately or wait for it to appear in Windows Update as a high-priority item. It will take several months for Windows Update to roll out IE7 to all XP customers, and anyone dissatisfied with the new browser can downgrade to IE6 by using the Add/Remove Programs control panel applet.

A blocking tool kit is still available for companies and organizations that don't use Windows Server Update Services and want to permanently prevent IE7 from automatically installing on PCs equipped with IE6.