You are using Excel 2010 (May for for Excel 2007 as well). You want to open each file in Excel as separate window. By default Excel 2010 (and Excel 2007) opens each file within the Excel Program. Excel 2010 and 2007 are designed as MDI applications.
This is not Microsoft supported option. Although this has worked well for me, use caution as this approach includes on undocumented registry changes suggested by many other internet search results. It was confusing to try out all the options and get the result correct. I wanted to share clearly given my situation what has worked.
Being able to open each file in new window means being able to run new instance of Excel.exe program, that means you are using more memory. So use caution while trying to open more files when you have your excel program configured for this situation.
To make .xlsx file open in new window.
"C:\Program Files\Microsoft Office\Office14\EXCEL.EXE" /e "%1"
You should see your registry changes similar to below pictures after change has been made:
Now give it shot by open the “.xlsx” files, you will see each file is opened in new window.
Beware each Excel.xxxx registry key is for each type of file that Excel as association with.
For other type of extension based files fine below nodes and based on that I guess you can figure out your other type of files that you want to open to be configured the same.
|File Type to Open||Registry sub key||File Version|
|For .xlsx||Excel.sheet.12||Excel 2010 file|
|For .xls||Excel.sheet.8||Excel 2003-2007 file|
|For .csv||Excel.CSV||Comma separated file|
Happy Excelling with more windows!