IE's inclusion with Windows also allows Microsoft to put tools in the OS that apply directly to the browser. For example, it offers so-called slipstream installation, which enables IE to be deployed as part of the Windows image that IT professionals create for corporate desktops. This eliminates the need to install the browser separately on each machine.

Microsoft has also offered, as part of the Group Policy settings in Windows, the ability to set policies for IE across desktops, which makes it easy for corporations to set security policies that help prevent malware from getting inside the firewall or sensitive information from going outside it.

Before Mozilla's Firefox browser started gaining traction among consumers several years ago, IE had been the standard browser for so long that many corporate applications were built to run on it and the Web protocols it supported, which -- until IE 7 and the forthcoming IE8 -- weren't always industry standard.

In fact, many companies that built applications for IE are still running IE6 to retain compatibility, analysts said. And even if they have updated to a newer version of IE, they use Window's Group Policy settings to render applications as if they are running on IE6 because they would not work otherwise, said Matt Rosoff, an analyst with Directions on Microsoft.

"A lot of corporate Web applications were built to display best or display online in IE6, and to rewrite those applications is more hassle than it's worth," he said.