The feature that protects against fraudulent Web sites, new in IE 7, in some cases could bog down computers running Windows, according to an article on Microsoft's support site published Tuesday. This could happen when a Web page contains many frames or when a user browses many frames in a short time, the company said.

"When you use Windows Internet Explorer 7 to visit a Web page, the computer may respond very slowly as the Phishing Filter evaluates Web page contents," according to Microsoft. "Internet Explorer 7 evaluates the whole Web page when you browse a frame. Therefore, CPU (central processing unit) usage may be very high."