How To Get Compare Plugin Back Into Notepad++

Go to notepad++ plugins from below site
http://sourceforge.net/project/showfiles.php?group_id=189927
Download ComparePlugin from below site
http://sourceforge.net/projects/npp-plugins/files/ComparePlugin/
Inside the downloaded zip file, you will find the ComparePlugin.dll. Unzip and place this into your Notepad++ plugins directory (which is usually at C:\Program Files (x86)\Notepad++\plugins)

Now open 2 files which you want to compare using notepad++
In the Notepad++ top menu, you will see Plugins
Click Plugins-->Compare-->Compare

That's it...:)