How to Clear Past Items from the Notification Area in Windows Vista

This article describes how to clear the Past Items list in the Customize Notifications window.

Clearing the items in Customize Notifications dialog

 The script can be run in Windows XP and Windows Vista systems.

To clear the Past Items list manually, follow the steps below: Do not forget to take he registry backup. 

• Click Start, type regedit.exe and press Enter
• Navigate to the following branch:

HKEY_CURRENT_USER\Software\Classes\Local Settings\Software\Microsoft\Windows\CurrentVersion\TrayNotify

• Delete the values IconStreams and PastIconsStream
• Quit the Registry Editor
• Open Task Manager (taskmgr.exe), click the Processes tab
• Select Explorer.exe, and then click End Process
• In Task Manager, click File, click New Task, type explorer, and then click OK.

The issue will be fixed. For more details Click Here