Is my Riva flv file encoder broken or what?

I am *very* *very* peeved at my Riva flv file encoder because it WON'T WORK NO MATTER WHAT I DO. Every time I try to change an flv file-- an inuyasha episode I downloaded, for example-- to something else, like an avi file or a mpg, it gives me an error message saying something about a video codec not being supported. It doesn't help that I know next to nothing about file conversion--or what the heck a codec even IS--; I just figured out how to use Riva on my own when I learned about flv files and the DownloadHelper extension on Firefox... and I know it's not the inuyasha episode that has something wrong with it, cause it does that with EVERY single video I've tried to encode for months.

I just recently got a new laptop, and its been doing the same thing on that too! I've tried other file converters like SUPER, but I just can't figure them out or they just don't seem to work! The other ones keeping spouting some nonsense about acronyms that start with FF*insert rest of extremely long 6 or 7-letter acronym here* and ME*insert rest of extremely long 6 or 7-letter acronym here* and audio, video, and file output codes or something like that!

First of all, what the heck IS that stuff, and secondly, is my Riva broken? I mean, it's not only totally not working on ONE, but TWO computers. Thirdly, is there some other working flv file converter that makes sense or can my Riva be fixed...? No matter WHAT I do, they will not work...

And I just want to do one stinkin' fandub, THAT'S ALL I KNOW! Please help me....?