Virtualdub is showing "missing codec" when I play a WMV movie even though the WMV plugin is in the plugins directory

According to Virtualdub, "the WMV plugin only reads the data from WMV/ASF files, it does not include the decoders.  VirtualDub uses VfW Codecs only, so you need a suitable VfW Decoder. DirectShow filters, as used by WMPlayer don’t work here".  One way to tackle this problem is to install ffdshow-tryouts and make sure you enable the WMV decoders under "VFW Configuration" -> "Decoder" -> "Codecs".  You can find ffdshow-tryouts here.

In my case however, I know that I have the ffdshow decoders since I use Media Player Classic - Home Cinema which comes bundled with the K-Lite Codec Pack.  So I did not want to go and re-install the ffdshow decoders all over again.  In this case I clicked on [Start] - [All Programs] - [K-Lite Codec Pack] - [Configurations] - [ffdshow VFW interface].  You should see something like this after selecting the Codecs menu:

I simply scrolled down to WMV3/9 and clicked on the Decoder to switch it from "disabled" to "libavcodec".  After restarting Virtualdub, I was able to see the WMV movie.

NOTE:  There is a similar configuration menu under "ffdshow decoder configuration" that looks identical to the screen shot shown above.  Changing the WMV3/9 format over there will not resolve the problem.  You have to do it using the "ffdshow VFW inteface" as shown above.