I recently purchased MS Office 2016 and am running it on my desktop Windows 7 machine. I have unchecked the protected files tabs and have tried both double clicking on an old .xls file and trying to open it from within Excel 2016. I get two messages,
the first that Excel is unable to open the file, and the second saying that the file is corrupt or read only, etc. I understand that the new Excel uses the .xlsx extension, but when I try to change the extension on the old file I'm told I need to be the administrator,
which I am. That message just repeats without giving me a chance to enter my administrator password, or any way to prove I'm the administration. Finally, I tried Microsoft's instruction to use the "change" option under uninstall for MS Office 2016, both
local and internet and basically reinstalled Office. Still unable to open those old Office 97/ 2003 Excel files. Any help appreciated.