I edited my films, but the problem is that it is mkv. It can’t import in Windows Movie Maker.
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Hamster Video Converter: Batch Video Conversion Freeware For Windows
Use VirtualDub and forget about WMM. It can be tricky at first, but it is quite good.
Windows Movie Maker CAN import AVI video files. Like the other commenters have said, MP4 and MKV will have to be converted using video converters, such as Format Factory or Hamster.
probably the easiest thing to do would be to convert them. I use http://www.mediaconverter.org. If you have a lot of files to convert I would suggest a batch converter like Prism from NCH software. These are my personal favourites but a google search will find exactly what you need
Convert them using a free program like AnyVideoConverter
With installation of free download MKV Codec Pack, you can also play MKV files with Windows Media Player, Windows Media Center, and trace to Windows Media Extenders (like the Xbox 360) and to UPnP devices (like the PlayStation 3). Fortunately, you won’t lose any quality when watching MKV files on your PC or through a Windows Media Center extender.
Besides, some component MKV Codec Pack support MKV file containing HD H.264 video with surround sound AAC audio and can also include advanced cinematic extras such as multiple audio tracks (e.g. director’s commentary), multilingual subtitles, chapter points, bonus content and more.
DirectShow splitter to sparse mkv files
final is to convert to a recognized movie format.