Some time has gone since my previous tips for making video thumbnails work in Windows 7. For some reason these tricks doesn’t seem to work in Windows 7 (not at least in 64 bit). Here’s a guide to fix the thumbnails in Windows 7 (probably works in older versions too!)
Fortunately, there is an easy way to make mkv files show the thumbnails, just install the latest MKV on Windows 7 from divx. Now you are probably thinking that you don’t want to install divx — it’s so 90’s. Fortunately, you don’t have to install anything extra just install the parts you need (meaning that you don’t need any codecs).
The following picture shows the necessary parts you need to have mkv video thumbnails in 64bit Windows 7. This probably works for 32bit too.
You will also have to install 64 bit video codecs. I prefer ffdshow since it basically contains video codecs for every possible video, in addition it supports hardware accerelated video decoding. You can install ffdshow from here. Just select the 64 bit version under SVN Builds. Notice that the 64 bit ffdshow codecs are still experimental so they might prove to be unstable…I think choosing the ”H.264 Decoder” and DivX codec in DivX installer might work just as well for some people. To me it really doesn’t matter so much since the 64 bit codecs are used only for thumbnail generation. The video player I use (media player classic home cinema, available here) is 32bit and therefore it uses 32 bit codecs. Actually, the media player home cinema is bundled with internal h.264 decoder.
EDIT:Installing the direct show filters is no longer possible. One must install DivX Plus. Only the codec pack is mandatory for thumbnails.