This is just a thought, as I don't have the time or stick-tuitiveness to volunteer:

The end product you want is a MIDI. It shouldn't matter what programs people use to create it.

If it looks funny when you import it into Noteworthy, it may be Noteworthy that makes it look funny. If it sounds right, it shouldn't matter. In other words, if you listen to it and it sounds fine, then import it into Noteworthy and exclaim "Holy Crap - all those dotted quarter notes should be half notes!" it might just be Noteworthy that did something weird.

NOTE: I'm not fond of Noteworthy. I don't like how many steps are required to enter notes and find that Noteworthy-created MIDI files often have shortened note lengths and skewed placement, both with re-play and when I look at it in Cakewalk.

Mary, it may be a pain in the neck, but you can right-click on the image of the sheet music to save it, then make it your wallpaper while you're doing the MIDI. (I have no problem having 2 windows open when using Cakewalk, but maybe it's just that the size of the two programs are too big to run together on your machine?)