In the file manager of choice, create two new directories. One will be the source and the other the destination of the thumbnails. Name 'em whatever you want. Copy (not Move) the source files - your originals to the source directory. While it is DIFFICULT to overwrite them, it is not impossible.

Now open Photoshop.

Name the action, and click Record.

In this case there is no need to set a function key, though this can be very useful for other actions you might want to create - even simple things like clearing memory and clipboard.

The action will show up in the Actions palette and Record Icon will automatically be selected.

Every gesture you make will now be recorded until you hit the Stop Icon to the left - the one with the square.

Set the size of the thumbnail you want.

Hit OK.

The Save for Web window.

1. JPEG settings.

Click OK.

When the file requester comes up, direct it to the destination file.

The window will close automatically.

Click on the close [X] icon on the thumbnail window.

Click the icon with the square to stop the recording.

The steps under "Thumbnail" should look as they do on the left.

Thumbnails can be edited and modified by clicking on the triangle in the circle under the [X]. With short Actions, it is simpler to delete and re-record.

Make sure when the requester opens, that the Action just created is showing under Play.

Source offers "Open Files" and "Import", as well as "Folder" so make sure that Folder is selected. The same with Destination below.

Click on "Choose" in each case to select your Source and Destination folders.

You probably will not have to check the options unless you are using an old Action that is looking for a different directory, or you have colour management set up to check on the embedded profile of each image.

Click OK and go find some tea and chocolate while the process grinds on.

The thumbnails will be in the Destination directory when you return.