Problem solved - used command fsck -y "hard drive name"

When it tells you to run fsck, do it. You will be asked for a password.

See: https://help.ubuntu.com/community/SystemAdministration/Fsck

Note that you need to tell it what to check. It should look something like
fsck dev/sda1

I believe that you can also change fstab to change 01 and 11s at the end of
the line to 00, but have never tried this as fsck has always worked.

One final thought, don't shutdown that way!

Yeah, I found fsck command.
You meant forced shutdown? What should I do in future if my computer crashes?

It all depends on what you mean by a crash and when it occurs. If you
are booting then it can't be helped sometimes. If you are at a command
prompt or in the GUI then you can usually isolate the problem and
recover.

I do not know a lot about Ubuntu, or Linux, been using it
about a year now.

One thing I learned is how to shut down or reboot a frozen Linux operating
system.

Here is a copy and paste from my notes:

It may sometime happen that our Linux powered system hangs completely and the
only option available is to shut down the system the crude way via the power
button.

Using the power button to shut down a frozen system can severely affect your
Linux installation, specially if you initiated the shut down when data was being
written into the hard disk.

Linux has an option for a safe restart or shutdown.

Hold down Alt+Sytem requirement. If you are using a laptop with the system
requirement accessible through the function keys, use the Alt+Fn+Sys Req
combination.

To restart, type REISUB in one go.

To shut down, type REISUO in one go.
What it does:

With every keypress of REISUB or REISUO, you initiate an action.

R: Switch the keyboard from raw mode to XLATE mode

E: Send the SIGTERM signal to all processes except init

I: Send the SIGKILL signal to all processes except init

S: Sync all mounted filesystems

U: Remount all mounted filesystems in read-only mode

B/O: Immediately reboot/shut down the system, without unmounting partitions or
syncingSafely Restart a Frozen Linux System with Reisub