Unable to install GRUB...This is a fatal error

[Ahmad]

I followed the Ubuntu installation guide from https://ubuntu.com/tutorials/install-ubuntu-desktop#1-overview. First attempt, I made a new partition at my C drive with 30GB space. Then, in the installation type phase, I selected something else from the options and installed Ubuntu in that drive. After installation was completed, it gave a success message saying remove the USB and restart the computer. I did it but nothing was installed. It seemed that I hadn't installed Ubuntu at all.

I tried to install Ubuntu alongside my Windows operating system. This time, half way through installation, it gave an error which read: Unable to install GRUB...This is a fatal error.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15.2
ProcVersionSignature: Ubuntu 5.4.0-42.46-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.445.1
Date: Sun Nov 29 12:25:01 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed maybe-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)