Q. How can I view one Excel spreadsheet and another non-Excel worksheet at the same time?

Depending on what version of Windows you have, you should be able to open one of your sheets, then bank it to either the right or left so it takes up half of the screen. Next, do the same with the other sheet in the opposite direction. You should now be able to view both simultaneously without one minimizing. 

Here's a link to specifics on viewing documents side-by-side for Word 2010 and Word 2007

For specific instructions using Word 2016, click here.