The file is Video_TS. Does anybody know what I can convert this with. I tried Mkw, didn't work.

like you said, you downloaded a DVD.

The DVD filestructure has a Video_TS folder and inside that folder various .vob . ifo .bup

No need to convert anything here! Just burn the filestructure as a new Video DVD with Nero or the burning software of your choice.

MKW/SHN or FLACfrontend are only used for Audio Shows to compress the WAV-files and reduce the overall size by ~40%. MKW and FLAC are basically compression tools like WinZIP or WinRAR that are just optimized for audio files.

It wouldnt make sense to compress a DVD thou. The MPEG2 video is already compressed and so is the AC3 audio. So a compression wouldnt reduce the actual size that much and that's why there is no additional compression like FLAC used to spread DVDs over bittorrent.