Save picture as ‘Windows picture and fax viewer’.
At bottom right of picture, click ‘closes this program and opens the image for editing’.
That takes you to the ‘paint box’.
At top, click ‘image’, then ‘stretch/skew’.
Enter required values for ‘horizontal’ and ‘vertical’.
If not happy with the result, click ‘edit’, and then ‘undo’.
When happy, click ‘file’, and ‘save as’, using a new name.
It’s very important to save with a new name, otherwise the original will be lost as the new size.
This one, I’ve called ‘30’, because I reduced the vertical size to 30%.
Have fun !