Just a quick little screen recording here. It shows how to use flvmdi from the commandline. The Explorer extension I use can be downloaded from the Microsoft website, it is called 'Open Command Window here'. I find it very useful as it enables you to open a DOS prompt at almost any location.
*** UPDATE ***
I have just noticed that the seek is not very accurate with this video. I think that's because I have encoded it with very few keyframes. FYI this video is also served via the PHP method posted previously.