There is no .cpl file, it is a standard .dll. And did you used the "officially unreleased" 64-bit version? It is a must on x64.
Windows Explorer is able to display files and folders using various methods. One of these methods uses thumbnails. Windows Explorer can extract thumbnails from images, animations, web pages, and some Microsoft Office files. Fortunately the Windows Explorer is able to work with 3rd party plug-ins and display thumbnails for virtually any document type. The extension available on this page allows thumbnail extraction for all document types supported by RW tools, including images, icons, static and animated cursors, and supported 3D formats (U3D, R3I, and 3DS).
Version 3.0 of ReaWolrd Thumbnails is capable of displaying thumbnails created in RealWorld applications up to version 2010.1.
Windows XP, Vista, and Windows 7: RWThumbnails32.msi
Windows x64 editions: RWThumbnails64.msi
You must pick the correct version for your Windows. 64-bit will only work on 64-bit systems and the same is true vor 32-bit systems.
There is no .cpl file, it is a standard .dll. And did you used the "officially unreleased" 64-bit version? It is a must on x64.
No control panel here, either. Windows Vista 32.
Great program.
Is there any way to add support for additional file types?
No, it is supposed to provide thumbnails for file types created by other RealWorld tools. If you want to create thumbnail extractor for your own file types, you can use the Microsoft's interface.
Haven't Used It Dad Will Not Let Me Download And Install It!

best one...
Just installed the x64 version on my Windows 7 Ultimate machine and no control panel item shows up. How do I configure it without a .cpl item?
for 64-bit Vista, please use this command to show the control panel:
control.exe "C:\Program Files\RealWorld Thumbnails\RWThumbnailsProxy.dll"
when I tried to install it there was no list of file types to check
Work for all format except .ico file ...
It's seem impossible to replace the default thumbnail handler ...
Find out how Vista icons differ from XP icons.
See how RealWorld Icon Editor handles Vista icons.