Resize multiple pictures in their existing locations with Irfanview

How to resize multiple pictures in existing locations with Irfanview (v4.35)

I have a few hundred pictures from a digital camera I want to get smaller and save some size. The quality is not really that important so losing image details is acceptable. Most pictures are viewed by zooming out to show the whole picture on the screen so it is a waste to have giant files for pictures that will never be zoomed in to.
I am reclaiming space on a friend's hard drive and the best utility to resize the photos is the Batch conversion utility built into IrfanView.

I wanted to replace the original files in their existing subfolders with existing date and time properties.
To do this I went to:
File > Batch Conversion/Rename

-The 'Output format' is JPG

- Advanced button > 'Set new size as percentage of original' to 30 (this is perfect for me, but it can be whatever you like)
-- CHECK 'Overwrite existing files'
-- CHECK 'Create subfolders in destination folder'
-- CHECK 'Save files with original date/time'
-- Click OK

-The 'Output Directory for result files:' must be the same drive as the one the pictures are on (for most people this is C:\). In my case it was D:\ because I have a partitioned drive where there was a Pictures folder.

I had to CHECK 'Include subdirectories (for 'Add all', not saved on exit)' in order to get all the pictures in any folders deeper than where I was viewing or adding from.

I suggest copying a few folders of pictures to a new folder and test this out before attacking the real job.

The final step is to click 'Start Batch' and wait for the magic to happen. It may take about a second or two for each picture you are processing so be patient, the results are worth it.