Solved! My macbook's CD/DVD drive has issues; boyfriend burned me a fresh version and it's running beautifully on the desktop.
Thanks ever so much to @pinoc, @Rudge, @NealManbear, @AS, @OldPolack for your patience and guidance! Even though it was a simple problem, I learned a lot in the process of trying to solve it.
For the record, Rudge's advice [see below] was new information to me (the whole time I assumed that I had permanently corrupted my computer when playing with the settings in root). Perhaps this can go into the FYI noobs section a little more clearly (or maybe it was there and I somehow missed it in my readings).
If you are not getting that far into the boot process, I would suspect
a) Your "CMOS" is not configured to try the CDROM as first boot location,
b) A bad burn, or
c) A hardware failure.