Very nice Astro!
I use DownloadHelper
to download .flv files (and it works on most sites I've tried it on) and a program called Super
to convert my .flv files to anything else (usually .avi), it comes with all the necessary codecs you'll probably ever need, including the FFDshow Codecs you mentioned Astro...
It's a good method as well, which doesn't need tinkering with the registry.
btw, I know the Super website looks all over the place and full of adds, but they are providing a really good video converter for absolutely peanuts (with no viruses or anything, trust me I've been using it for months now), so IMO we can forgive that