You can either use a Flash detector to check if the user has Flash 5 and force them to get it if they don't, or you can publish your Flash 5 file using Flash 4 syntax. Open the file in Flash and use Ctrl Shift F12 to edit the publish settings. In the Flash tabe select Flash 4.
Please don't email or PM
me Flash questions, that's what the Forums are for!
Please don't rely on me reading my PMs either. Email me about important stuff.