What to check in firewall settings during installation of ym 9

It would help a lot to know what the missing file is, but for your firewall settings, open the settings dialog box and click the "Exceptions" tab. It should display a list of programs that are designated to "Not block." If "Yahoo! Messenger" is not listed, you should add it. Click the "Add Program" button and enter the path to your Yahoo Messenger application. It may look something like this: C:\Program Files\Yahoo!\Messenger\YahooMessenger.exe