In Windows 7 “System and Security” control panel category, the Action Center lets you change User Account Control (UAC) settings. In User Account Control Settings dialog box, you move the slide bar control for notifications, and then you click the OK button. In this scenario, the dialog box doesn’t close, and no change is made. When the mouse pointer is positioned on the OK button, and you press ENTER, the dialog box still doesn’t close, and no change is made. Note If you click Cancel, the dialog box closes and no change is made, as expected. “This issue occurs when Microsoft Office 97 is installed on Windows 7. The installation of Office 97 makes a change to the registry that causes this issue.” To resolve this issue, change the registry setting. To do this, follow steps mentioned in KB978591.