Force Visual Studio to open special (e.g., Excel) files instead of calling another program

I'm debugging something and want to compare two Excel files that look identical in Excel. I want to view the source somehow and see what the differences are.

The problem is that Visual Studio (2010 and 2008) both use Excel instead of opening the file itself. Even if it'开发者_如何学Cs just a hex-editor view, how do I use Visual Studio to open these files instead of Excel?

If the file is in the solution explorer, you can right-click it and select Open With... Then select "Binary Editor" and click OK.

But if they are Excel 2007 files, just rename the file so it has a .zip extension instead of .xlsx and you can then unzip it and look at the xml directly.

Right click on the file --> Open with --> Select source (text) Editor (or whatever you want) --> click make default for this type of file.