I am using windows 2007, if I open 2 different excel files, one on each monitor, how do I do that?
As it is now, if I move one file to a monitor, the other one follows

Use the Start menu to open a second instance of Excel, and then get into the habit of using drag-and-drop (or Office Orb - Open) to open the second file, rather than double-clicking. You will probably also want to turn off "Show all windows in the Taskbar" (Orb, Excel Options, Advanced, under the Display section), to avoid problems with DisplayFusion.

There is another workaround that allows double-clicking to work, namely, disable DDE. This can cause other problems, and I do not recommend it. It's not that much more trouble to drag-and-drop vs. double-click.

You cannot easily link cells between different Excel files if they are different instances. I recommend the add-in below which works well with the DisplayFusion "Span across all monitors" Titlebar Button. With this add-in it makes it easier to use a single Excel instance on multiple monitors.

The Excel "Dual View" add-in can be found in this link.
http://www.xl-logic.com/modules.php?name=Downloads&d_op=viewdownload&cid=3