After hitting "Yes" on "Do you wish to continue?" I get

fsck from util-linux 2.20.1

/dev/sda1: clean, 166400/2444624 files, 906859/9765755 blocks

With a blinking cursor on the line below it. From here, the only thing I can do is power off and start up again, and I'm still in read-only mode.

Background:

I'm using a Toshiba Portege R100, a laptop that lacks a CD drive and can't boot from a USB stick.

I removed the R100's hard disc, plugged it into a Mac (over USB) that was in "Try Ubuntu" mode using a DVD,and then I installed Ubuntu onto the R100's hard disk.

With the hard disk back in the R100, on start-up, after the GRUB menu, with Ubuntu selected, it displays the Ubuntu logo then goes into "Low-Graphics Mode," covered here:

How to fix "The system is running in low-graphics mode" error?

In attempting to try the various fixes reported there, I have to use Recovery Mode, which leaves the disk, by default, in read-only mode.

And that's where I try "Enable Networking," which results in the blinking cursor (crash?).

I have also tried dropping to the shell and trying

# mount -o rw,remount /

which is the fix here, http://ubuntuforums.org/showthread.php?t=1870817

But that doesn't work. I just get a new prompt, as if I entered a return, and the system remains read-only.