Imagemagick batch convert all pngs in subdirectories to jpg

I have a folder with a number of sub folders in it which contain the images I want to convert from png to jpg.

I have tried.

cd d:\images

mogrify -format jpg \*\*.png

I tried slashes in both directions (I'm using windows 7).

but I just get invalid argument errors.

What should I do?

I'd really most value a simple example answer rather than a link to a 50 page image magick documentation if possible (I'm a newbie).