When you open a new tab in Internet Explorer 7, the You've opened a new tab message appears, and you're unable to turn off this option even though the option Don't show this page again is selected.
The preference may not be saved due to a script error in the res://ieframe.dll/tabswelcome.htm page. As a workaround, you may alter the registry directly or use the REG files below to configure this setting.
HKEY_CURRENT_USER \ Software \ Microsoft \ Internet Explorer \ TabbedBrowsing
You can automate the above using the .REG files available in the Attachments section of this article.