It's a not hard task as long as you get an easy-to-use FLV convert app.
Brorsoft Video Converter is a professional utility that convert FLV files to video supportable on portable device, media players or video editing programs with the best quality movie clips and audio. This FLV converter supports encoding FLV to popular video formats including AVI, WMV, MOV, MP4, 3GP, MPG, M4V, etc. format. And you can convert many video files in batches. Plus, it allows you to split output file and customize file size according to your preferences.
Step-by-step conversion guide: http://www.brorsoft.com/how-to/conve...-wmv-mpeg.html