I have recently started a new social network called [moderator: link to personal site removed; self-promoting your site is not allowed on the forums). I wonder if it is possible to integrate flash player to my social network so that my users can play the uploaded videos without problems.
Flash Player is a browser plugin, and installed on the client, not the server. What you'll need to do is detect whether or not the user has Flash Player installed. If it is installed you'll need to detect if it's enabled or not. If not, prompt the user to enable it. If it's not installed, notify the user they need to install Flash Player.