Files combined in a folder will usually automatically sort themselves out into numerical or alphabetical order. If you look at the combined files with that in mind, you may be able to see why they sort themselves into the order they do. I think you'd have to rename all the photo files in the folders to get them into the desired order in a single folder. Renaming many photo files individually would be a daunting task but there are programs that can rename entire batches of photos, for instance Irfanview (free) can do it.
You'd have to rename the photos in the first folder to perhaps '001 - 002 -003 and so on. If the end number was 020, then you would rename the photos in the second folder starting with the number 021 etc. Rename the photos in other folders in the same fashion. When all of the photos are numbered, they could be added together in the same folder for using in a continuous slide show. Photos would show in numerical order.
However, Irfanview can do something better than that. The slide show facility can add folder after folder of photos to a slide show in any order you wish them to display, even if some photos have the same file names/numbers as others. This can then be saved as a standalone 'exe' file, or as a screensaver. There is also the option to burn the slide show to a CD. This seems much more preferable than attempting to rename or reorganise the photos in the folders.
It's possible that other image file viewers/programs can do the same thing as Irfanview.
Edit: If you decide to install IrfanView, note that it comes with an option to install Google Toolbar and Desktop Search. Be sure to untick the option box during installation if you don't want these.
Edited by tellywellies (Fri Jun 22 2007 04:15 PM)