Free ware to convert FLV files to mpg?

Super, for any video conversion. Period.

U can also try Riva FLV Encoder

Just remember Super Converter (Freeware) for any Video conversions.

yep... Super is the best... also try FLV converter..

Why take trouble of installing a software
If it's a youtube video, then directly download converted mpgs using vixy.net
or use VDownloader to do the same job.
If you have a flv, then you can also try media-convert.com

(Of course I'm assuming you have a broadband )