Okay I was able to solve it finally. Here are reasons and directions of how to solve it.
REASON:
The above situation is due to preinstalled Windows 10 in UEFI mode and Ubuntu installed in LEGACY Mode.
SOLUTION TO WHOLE PROCESS:
1.0: Press F2 on boot and change RAID ON to ACHI and in boot menu disable secure mode.
- Make a UEFI only USB by formatting usb as FAT32 and copy paste the contents from Ubuntu.iso to that usb.
- Now press F2 to go to setup and manually add an entry to grub.efi
- Keep the manual entry on top so that the computer boots from this option
- Reboot the computer and you will be on the grub screen.
- Now on install option press e to edit and add the option for nomodeset or the desktop will freeze in Alienware because of NVIDIA graphics card.
- Now press enter and the installation will start.
- When you go to disk partition, select something else option
- Now select the unallocated space and make swap partition double the amount of ram.
- Now assign the remaining partition to /
- At the bottom on the same screen install the boot loader into the same / partition.
- Reboot and after installation select try ubuntu and perform step 5.
- When you get the desktop.
- Open terminal and install boot-repair
sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update
sudo apt-get install -y boot-repair && boot-repair
- Folow the steps and you will get both windows and ubuntu options in the grub.
Note: If you get the boot-repair is not in UEFI Mode screen in boot-repair app then it means you havent done step 2 properly. Thats the reason we made UEFI only usb to make sure that we are not in ACHI mode but in UEFI mode.
I have written the above steps from memory so let me know if any problem and I will try to help.