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