You would modify the flash file so that the last frame you want the viewer to see has an action script command:
getURL("http://www.creativecow.net","_top");
Make sure if you are using Flash CS3 you use ActionScript 2.0 or you will get a 1180: Call to a possibly undefined method getURL. error because getURL doesn't exist in AS 2.
If you are using CS3 and/or ActionScript 3.0 then you would use this method:
var request:URLRequest = new URLRequest("http://www.creativecow.net");
navigateToURL(request,"_top");
Abraham