Ok, more investigation reveals that the "Normal.dotm: File format is not valid" message happens when I try to open Excel on any of 3 different computers. Therefore the offending version of file 'Normal.dotm' must be somewhere common to all 3. The main possibility was Dropbox so I searched there and, surprise surprise, there is a version of the file. (I assume this is not where it is supposed to live?) So I deleted the file (hang the consequences, lets live dangerously!) then opened Excel on each of the 3 computers. No message. All good so far. But each time I've done this over the last month, it has reappeared a few days later, I think when I create a new file with Word...I'll test that over the next few days and report back. The bigger mystery still remains why Excel goes looking for or is sent to a Word 'template' instead of the excel version of template. Have I pointed it in the wrong direction at some stage perhaps? I'll keep looking and report back. Thanks