Firstly I have tried to approach Irfanview,but it seems impossible to register with them. However this thread also includes other matters.
A time ago we took a holiday and I started to edit the numerous photos. Amalgamating the items from our cameras and other things happening led to me deleting wrong files. I found the missing files, fortuitously on an external disk, as I had recently upgraded my computer, by using Recuva. What was recovered bore varying file names, had duplicated views and had been audited for aspect size and so on.
I batch renamed all to be sequentially numbered in ascending order of date taken, but items,identical except for different original file names or editing, at the same time and day, have widely different sequential numbers e.g 13 & 252.
I cannot think why this has happened.
Please; I hope someone can help.