closing konqueror didn't work but i succeeded after changing to runlevel 1 (got the idea in a forum post here). gave umount and mkfs commands from runlevel 1 command line. (for newbies like me, you must edit /etc/inittab to change from runlevel 5 to runlevel 1.)
there was a lot of response to mkfs, so i suspected success. to my dismay, i couldn't log in on my user name or find my home directory.
nor could i create new users. iceweasel's equivalent wouldn't run on root either.
it's not all that bad; not much on that home directory that i'll miss, and i'd planned to reinstall fedora too. the experience had taught me some things...