Flash / Animated Gifs

Hi all,
I am currently redesigning a website for someone, but they are not too keen on the use of Flash. This includes external company banners, as well as nav etc on their own site.

Except for the nav side of things, is there anyway that a Flash banner can be automatically replaced by an animated gif, if the user does not have the Flash player.

I am looking for a way that this can be done without A) The user being redirected to a pure HTML version of the site, as it is not a full Flash site to begin with , and B) without the user getting prompted to download Flash Player.

Any help/suggestions would be greatly appreciated . . . . .

cheers