I succeeded last year in scripting a powerful flash detector using java-script and vb-script.
you can detect the needed flash version and if you want let the script spit out an image instead of the flash if the flash version was not found.
furthermore there is no more need to write 5000 charachter long object tags for the flash to embed into html since the script takes care of this and setting are beeing easily set through the script's properties.
till now it was only tested successfully with the latest mozilla firefox, mozilla and internet explorer 6
download the zip file and check out the read-me file in the installation info folder.