A dvr-ms to flv conversion generally refers to export of Microsoft Digital Video recording files (.dvr-ms) to Flash video content (.flv).
Any of the multimedia converters listed below should be capable of this conversion. Linux users can use the command line FFmpeg video encoder that is also able to convert DVR-MS videos to Flash:
Open bash (terminal) and type:
ffmpeg -i /path/to/your/file.dvr-ms -vcodec copy -acodec copy /path/to/your/newfile.flv