Conversion between various video & audio formats

> Could anyone advise me a good software to do conversion between any video
> &
> audio formats?
>
> I have used "Total viedo convertor" to convert a .wma file into various
> viedo formats (.mpg, .flv, .avi), but none of them can be posted to
> Facebook
> or Youtube (the latter 3 viedo formats should be acceptable to Facebook &
> Youtube). I guess the failure is due to the source file is an audio file
> &
> convered into a viedo file, not a conversion from 1 viedo format to
> another
> viedo format. Could anyone kindly advise?
>
> Many thanks!