If you want to open two Excel 2007 windows, each with different spreadsheets, you’ll need to check out this tip. I have two monitors, and I need to use two spreadsheets at the same time. By default, you can’t open two excel instances at the same time. Here’s how to change that.
http://blog.sadasystems.com/2009/07/open-multiple-excel-2007-windows.html
In case that site or file is unavailable, I am hosting it here myself. Thanks for the tip!