You can open 2 separate windows with a separate Excel spreadsheet in each.  This is not the default behavior of Excel and it tries to keep all your spreadsheets within one Excel window although you can swap to see which spreadsheet is on top.

The trick is that you have to open 2 instances of Excel.  Here’s how:

1.  Open your first Excel spreadsheet.

2.  (This is the trick) Open another copy of Excel from the Start Menu shortcut or right-click on the icon in the task-bar and choose ‘Microsoft Excel 2010’ or 2013 etc depending on the version you have.    Do not go file -> Open from this window or double click to open the second file you want – this will just open that document within the same first excel window.

 

 

Excel_taskbar_screenshot

3.  Drag this window to the second screen or correct position.

4.  Open the second workbook you need by going to File -> Open on the second Excel Window.

 

This is really handy if you have multiple monitors and need to compare 2 spreadsheets or copy and paste information from one to the other.