Irfanview[/url]
Select File > Batch Conversion/Rename
Under Name pattern enter $F (this will save the new file with the original filename and directory structure)
Beneath this enter the Output directory where you want the thumbnails saved (do not use the current directory as the resulting files will have the same name and directory structure and will not save)
Mark the tickbox for advanced options and then select the Advanced button.
Tick the Resize box and enter the new size you want the resulting file to be.
Under Miscellaneous tick Create sub folders in destination folder.
Click OK
Tick the Include subdirectories box on the left hand side.
Locate and highlight the folder where your photos are kept in the directory box (top right)
Click Add all button
Click Start Batch button
This works for me.