Schare's betting that the improved IE 7 security will meet the bar set in 2004 by Windows XP SP2, which was given credit by most analysts for stymieing some kinds of attacks.
"I'll never come out and say we'll never have another vulnerability, but IE 7 is more secure. We've changed the underlying code and we've put in defense in depth features."
Internet Explorer, which once was used by 95 percent of surfers, has been under a small but steady siege by rivals such as Firefox since that open-source browser's debut in 2004. In the 14 months since Firefox 1.0 appeared, IE's share has dropped to between 85 and 87 percent.
Schare said that Microsoft wants some of those people back.
"Our satisfied customers, the people who are running IE 6, those people are going to be thrilled with IE 7," he said. People who switched because they wanted a non-Microsoft browser may not return, but "the people who decided to change [to Firefox] for some of its features, not because they were dissatisfied with IE, those people will find a better Internet Explorer in 7."
Microsoft also released its Windows RSS Platform Tuesday, taking the technology formerly available only in Windows Vista to XP so that developers can deliver news feeds to customized Windows applications running in the older operating system.
The Windows XP edition of IE 7 Beta 2 Preview can be downloaded from the Microsoft Web site.
For more information, including a closer look at the browser's features, see Microsoft Issues Public Beta Of IE7 For Windows XP.