I created an ext4 partition while installing Ubuntu, and used on the mount '/'. Finished the installation and restarted, after which it prompted to remove installation media. I did, and then the computer stopped responding. So I manually turned it off, and now I can't get any option to boot up Ubuntu. Takes me directly to my windows 10 lock screen.
In the setup I encrypted my home drive.
Also, later I tried to boot up after installation from the CD, and I couldn't. The screen froze at this-
Graphic drivers are not a core of this problem, Windows 10 is :)
I assume you have a PC that's new enough to have UEFI bios. Windows 10 does two things that make installing anything beside it problematic.
1) when a FastBoot option is enabled it blocks EFI partition and prevents you from installing GRUB.
To solve this disable fastboot in both UEFI and in Win 10 (google for this option as it's hidden well). After Ubutu is installled you can re-enable it in UEFI (not in Win10)
2) EFI partition has a convinient option, when you have more than one OS UEFI shoud ask you which one you want to use on every boot. BUT M$ made it so Windows Boot Manager makes itsel default stripping you from your right to choose.
There are some ways to steal your hardware back from M$. Firstly: google your notebook / MB model to find which key to press on boot to force EFI boot selector to show. For my MSI it's F11.
If you have GRUB there just select it and then google for how to make it default (hint: Windows CMD is best for that).
If you only have Windows Booot Manager, disable FastBoot and reinstall Ubuntu.
As for @Ashu solution use that only when you get a hangup or black screen when booting Ubuntu. I you're on Skylake/nvidia expect that to happen :)
If there is no fastboot option in bios then just disable it in Win 10, it should suffice.
Now we have to make sure that Win 10 boot via EFI not MBR. You will have to google a bit since I have no time today to do it for you...
Now use any software that can handle disks and partitions on Win 10. Default partition manager should suffice. Check if you have an EFI partition (it should be the first one on first drive and have around 100 Mb). If yes, mount it. It should go like:
open cmd as admin
diskpart
sel disk 0
sel part 1 (efi part)
assign letter=b
exit
taskkill /im explorer.exe /f
explorer.exe
Now you should have an EFI partition mounted in My Computer. Look inside ( if explorer tells you that you can't then use CMD as admin). Inside should be an ubuntu folder. If it's there do in CMD as admin:
bcdedit /set {bootmgr} path \EFI\ubuntu\grubx64.efi
(CAUTION: check if your .efi file is grubx64.efi - if you have SecureBoot enabled it will be named differently). Reboot and welcome GRUB.
If there is no such folder, reinstall Ubuntu with Fastboot disabled. Also you may try to disable SecureBoot in bios.
RESULTS.txt. Post that file to a pastebin site and post the URL to your document here. This will give us more details about your configuration, which is required to base an answer on more than guesswork.