Thank you for your quick response. If I understand you correctly, it wasn't a download that I was trying to quit; I was just trying to quit iTunes so that I could open it again and confirm whether I'd successfully moved my iTunes media to an external drive (to save space on my overcrowded iMac's internal drive). if you have time to click on the article highlighted at the top of this discussion ...
Learn about iTunes for Mac: Moving your iTunes Media folder
... it might make things more clear. It appears that I'd completed the process of copying my iTunes media files to the external HD, and I was trying to finish up by deleting those same files (but not the "libraries") from my computer -- that is, dragging my original iTunes media folder to the trash and then, as instructed, quitting iTunes and seeing if I could open it up again without any problems. (If so, I couid then empty the trash -- which I have NOT done yet, fortunately.) But when i tried to just quit iTunes, it was almost 48 hours ago and it's still trying! If I move the iTunes Media folder from the trash to the desktop and then "force quit," would it still be a test of whether I'd copied everything successfully to the external HD? (I guess that would be the backup I need, but, yes, I also use Time Machine, and last did that backup just before I started this process two days ago.)
Thank you again ... anything you can tell me would be appreciated, since (as you can probably tell) I'm trying to be extra-careful.