Having done the above - then the attached might be useful...
I had the mer1ho_0xxx , 2ho, 2no and 1no folders on the root of a drive called H
If you unzip the attached into the root of H - you will find img2png.exe ( hope you dont mind me repackaging it with these little bat's Bjorn - img2png is from here - http://www.mmedia.is/bjj/utils/img2png/
) - imgbat.bat (my bat to run img2png on a load of files, and then tuck the raw img's into a 'raw' folder to keep things tidy.
AND - four bats - one named after each of the folders above.
Now all this HAS to run in the root, and HAS to be on a drive called H:. If you can dump it all onto an external drive and set that to H: ( control panel, admin tools, computer management, disk management ) - or any drive ( that isnt C: obviously) then do it - otherwise you'll have to open each bat and search and replace every h: for a whatever: you're stuff is on.
Just run them - it'll plough thru the downloaded data - copying my bat and img2png into each folder, running it, then backing up and doing the next folder.
I'm sure there is a more glamorous way of doing it - but I did the brain-dead way of having a massive long bat that will simply do this for 1500 sols worth of data. 1500 was big enough to not have to worry about rewriting it in the near future, but no so big that the BAT file ends up too large.
I've checked, and as long as you have those four folders on the root of H - it works beautifully. Expect about an hour for a ho data set, and about two hours for a no data set. - Since about 1030am, I've done two HO's and one N ( and that's in 3 hrs 26)
Hope these are usefull. Combined with the wget, and the bats above - this setup will let you download and process about 30,000 images.
Just as a double check - you need to have the highlighted files in the root of a drive called H to run them as they are.