I recently had this same issue. You probably had unsuccessfully downloaded a corrupt plugin (i.e. from Real Player, Quicktime, Winamp). The result of such a plugin could affect .exe, .pdf, or other files depending on what application you were using.

Follow the following steps in order to resolve this issue:

Go To Start
Go To Run
Type Regedit
Go To HKEY Local Machine
Go To Soft Ware
Go To Microsoft
Go To Internet Explorer
Go To Plugins
Go To Extension
Right click on Extension and click on delete

I was initially hesitant to delete this file. But I found confirmed that this file is not needed.