For Windows XP users with IE8 Beta 1 already installed, Windows XP Service Pack 3 and IE8 Beta 2 would become permanent, said Jane Maliouta, the deployment product manager for IE8 at Microsoft. "You will still be able to upgrade to later IE8 builds as they become available, but you won't be able to uninstall them," she said.

Incompatibility Issues

Developers will need to be careful because IE8 Beta 2 will not work with several key services, applications and add-on programs, including certain versions of the Google Toolbar, RealPlayer and Skype, and is even incompatible with Microsoft products and services, such as Visual Studio .NET and Windows Live Mail. IE8 Beta 2 users also are currently unable to view movies on demand from Netflix, though Microsoft said the two companies are working to resolve the compatibility issue as quickly as possible.

Maliouta strongly encouraged those who have already downloaded IE8 Beta 1 to follow several steps before installing the new Beta 2 version. First uninstall the Beta 1 version and SP3 for Windows XP, followed by reinstalling SP3, and only then install IE8 Beta 2.

"If you have IE8 Beta 1 installed, the IE8 installer will automatically uninstall any earlier versions and then install the latest version of IE8 Beta 2 for you," Maliouta said. "You will be prompted to reboot twice. The first reboot is to remove IE8 Beta 1 from your machine and the second one to complete the IE8 Beta 2 installation."

According to Microsoft, IE8 Beta 1 was only intended for use by developers. Consumers running Windows XP need not worry about downloading IE8 Beta 2 so long as they did not install Beta 1.

However, consumers testing IE8 Beta 2 on their Vista-enabled machines must jump through a few hoops should they decide to revert to IE7. According to Microsoft, they'll have to click the Start button, type "Programs and Features" in the Start Search box, and click Programs and Features in the Programs list. Then in the Tasks pane, they'll need to click "View installed updates," select IE8 Beta 2 and then click "Uninstall."

Dueling Releases

The relatively unpolished state of IE8 Beta 2 is not all that unusual. Early versions of Firefox 3 likewise were subject to various compatibility issues and performance limitations.

Both Mozilla and Microsoft are doing all they can to gain browser market share. For example, Mozilla's recent release of its "experimental" Ubiquity plug-in is an attempt to steal some of the thunder from some new features destined for IE8, called Accelerators and Web Slices. For its part, Microsoft has already added several new capabilities to IE8 Beta 2 that mimic what Firefox 3 already has on tap, including the rival browser's so-called "AwesomeBar."

Mozilla's campaign to set a world software-download record for Firefox 3 earlier this year has increased the pressure on Microsoft to turn the tide. Though the software giant has stabilized its market-leading share of the browser market in the last three months, Microsoft's numbers have fallen seven percentage points in the past 12 months, and 24.5 percentage points since August 2005, according to a new global survey conducted by Janco and the IT Productivity Center.