Plugin.ocx

Invalid or malformed Class Identifier: {06DD38D3-D187-11CF-A80D-00C04FD74AD8}

Specified Inproc Server is invalid: c:\windows\syswow64\plugin.ocx

When you update Internet Explorer, the Plugin.ocx binary is completely removed from Windows Server 2003 and Windows XP.
The Plugin.ocx binary is a private component of Internet Explorer without any public interfaces.
Plugin.ocx is used to host Netscape plug-ins as ActiveX controls. The functionality of Plugin.ocx was disabled in Windows Server 2003 and Windows XP for security reasons.
This update removes the non-functional Plugin.ocx code completely, after which the specified Class ID key becomes invalid and useless.
This issue is described in Microsoft Knowledge Base.

AMUST Registry cleaner will delete obsolete Class ID key.