[son_of_war]

возьми детект, который вставляет 6 версия - там она делает все на JS

<SCRIPT LANGUAGE=JavaScript1.1>
var MM_contentVersion = 6;
var plugin = (navigator.mimeTypes && navigator.mimeTypes["application/x-shockwave-flash"]) ? navigator.mimeTypes["application/x-shockwave-flash"].enabledPlugin : 0;
if ( plugin ) {

var words = navigator.plugins["Shockwave Flash"].description.split(" ");
for (var i = 0; i < words.length; ++i)
{
if (isNaN(parseInt(words[i])))
continue;
var MM_PluginVersion = words[i];
}
var MM_FlashCanPlay = MM_PluginVersion >= MM_contentVersion;
}
else if (navigator.userAgent && navigator.userAgent.indexOf("MSIE")>=0
&& (navigator.appVersion.indexOf("Win") != -1)) {
document.write('<SCR' + 'IPT LANGUAGE=VBScript\> \n'); //FS hide this from IE4.5 Mac by splitting the tag
document.write('on error resume next \n');
document.write('MM_FlashCanPlay = ( IsObject(CreateObject("ShockwaveFlash.ShockwaveFlash." & MM_contentVersion)))\n');
document.write('</SCR' + 'IPT\> \n');
}

</SCRIPT>

и дальше if (MM_FlashCanPlay) ... выводи свою флэшку или картинку