With the Group similar taskbar buttons option enabled in Taskbar and Start menu Properties, when you open more than one document in the same program and then minimize each document so that it appears as a button on the taskbar, all the buttons for that program are grouped together on the taskbar.
In some systems, the Windows Explorer and Internet Explorer taskbar icons may be grouped together even though they both have different executable names. This article describes how to fix this problem.
This happens if the Launch browser windows in a separate process option is disabled in the registry (BrowseNewProcess value). If the setting is disabled, all instances of Internet Explorer and Windows Explorer that you start are run in the same process.
You can fix the Taskbar grouping problem by enabling the Launch browser windows in a separate process option using the following steps:
HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Explorer \ BrowseNewProcess