Hyperlinks do no change colors after they have been clicked.
Cause 1: The same color is used for Hyperlink and Followed Hyperlink
Solution 1: Click the Design tab, click Colors and Create New theme colors, make the colors for Hyperlink and Followed Hyperlink are different
Cause 2: There is a bug in Microsoft Office PowerPoint for Office 2007
Solution 2: Clients must contact Microsoft to request a Hotfix for the issue. Go to http://support.microsoft.com/kb/2412275 and click View and request hotfix downloads.