Forget about running those commands. Let's take an easier approach.
Problem: Computer no longer boots -- grub bootloader doesn't seem to work anymore.
Solutions:- Try to repair grub bootloader and if that was the only problem then good chance system will work again.
- If that doesn't work, just re-install Linux Lite.
Try to repair grub first.
* Boot up computer using the live DVD/USB that you originally used to install with.
* Once it is running, open Firefox and go to this site:
https://help.ubuntu.com/community/Boot-Repair.
* Follow the instructions for the "2nd option : install Boot-Repair in Ubuntu"
* You will need to open a terminal (Menu -> Accessories -> Terminal), then copy/paste the commands shown into it and hit enter after each one.
* That will install and start the Boot-Repair utility.
* Follow rest of instructions, then reboot computer to see if it worked.
If that did not solve problem, then next easiest thing to do is re-install Linux Lite.
* Boot up computer using the live DVD/USB that you originally used to install with.
* If you have anything on the hard drive that you need to save (documents, pics, etc.), connect a USB to the computer, open the file manager and navigate to /home/les (or whatever your username is) and copy the files to the USB. Then close the file manager. Unplug the USB you just copied things to.
* Double-click the "Install" icon on desktop to start the installation procedure.
* When you get to part where it asks how you want to install, pick the option that basically says it will erase what's there and use the whole disk.
* It will automatically get rid of the old one and replace it with new installation and new partitions.
That's it.
P.s. If you did click on the hard drive to copy files to your USB, there is a possibility the installer may complain that the drive is mounted and it won't install. (Don't know if that will happen or not -- just trying to cover the possibility that it might.) If that happens, look on your desktop for drive icons. Right-click them and choose "Unmount" if that choice is available. If "Unmount" choice is not available, that means that particular drive/partition is not mounted -- so don't worry about it and right-click any others you see until you find the one(s) that do show the choice. Once that is done, you can try running installer again.
If you can't get that to work for some reason, just shutdown and boot back up again with your live DVD/USB and go directly to installation. Should work without any problems.