I'm unsure whether this is down to Excel (version 365 in my case) or the Win 10 OS,
but so far I've not resolved it.

Whenever I open a workbook from File Explorer (Enter, or double-click), it is
displayed maximised.

Other file types like JPG/GIF/PNG open in their associated application (IrfanView in
my case) at whatever size and position they last had. Similarly with TXT files in
either own editor, TextPad or using 'Open with' Notepad. Same with Word 365. So
far I've found only Excel has the issue. Saving at the preferred size makes no
difference.

Anyone able to reproduce, or have any idea what might be going on?

Terry, East Grinstead, UK