The 64-bit version of Windows Explorer is not able to load 32-bit shell plugins. That is the reason why it won't be able to generate thumbnails for some video formats. The solution is to run the 32-bit version of Explorer. That will be able to generate thumbnails. The thumbnails are cached, which means that the 64-bit version of Explorer will able be able to display them. Use the following command to run 32-bit Explorer: Start -> Run -> "C:\windows\syswow64\explorer.exe" /separate |