A number of users have asked how to share information between multiple windows that may have been opened via JScript/Javascript. There are a couple techniques you can use. The first involves passing data from the "parent" to the "child" via the URL. This will get the secondary window enough information to get going. At that point, the secondary window can get data from a database or somewhere else in the same way that the first window can.
One point to remember when using multiple windows is that they can get confusing for the user, especially if you keep opening new windows for each record, for instance. If you need independent pages, you may want to consider using a framed page instead.