You can create Report Templates and Import Templates in 2010, 2013, 2016, and Mac 2011 versions of ExcelTM. This allows you to import or attach files with .xls and .xlsx extensions.
When downloading Excel files (printable views and reports) from Adaptive Planning or other Adaptive Suite solutions, the files will always output to an .xlsx format. This format is supported in Excel 2007+ .
If you are running Excel 2003, you can download and view files. First, you must install the Microsoft Office Compatibility Pack. Here is the link to the download page: Microsoft Office Compatibility Pack.