Installation Issues alongside Windows 10 .. Please Help!

Hello,

I'm trying to install Zorin OS along side my Windows 10 OS and the installation was successful (around 80GB was allocated for Zorin OS).
But when I reboot my system, there is no option to choose between the two Operating Systems and my laptop boots directly to Windows. My hard drive space has reduced by 80GB and data occupying that much space is not visible in Windows Explorer.
Under Advanced System Settings, the only Operating System that shows is Windows 10.
Can someone please suggest how I resolve this situation? How do I roll back the Zorin installation and get back the hard drive space?

Thanks,
EK

First. Have you looked at Swarfendor's unofficial Manual for Zorin 15 here:
viewtopic.php?f=6&t=14361

It sounds like you are wishing to run Zorin as dual-boot alongside Win10.
To help people here to help you, can you describe the method you used to do your installation of Zorin.
Also which Zorin 15 did you Install i.e. Ultimate, Core or Lite?

If you are not seeing a OS chooser menu on Restart then something has gone wrong with GRUB during install.
I think I missed a step about where to put boot loader on my very first attempt to install Zorin as dual-boot way back. That saga is contained in this thread:
viewtopic.php?f=4&t=14247

Your best option is to install EasyBCD from NeoSmart - my video on dual-booting Windows 7 with Zorin 9 applies just as much - you should include a 512 Mb /boot partition at the start of the 80 Gb set aside for Zorin in which to place GRUB formatted to Ext4, then '/' System partition of 50 Gb formatted to Ext4, then an extended/logical partition containing linux swap = to double the amount of physical ram you have at the END of the extended partition and everything else in front, marked as /home formatted to Ext4.

You haven't stated if you are installing to SSD - if you are then all partitions should be formatted to Ext2 to extend the life of the drive - you also need to setup TRIM if SSD - Windows does this automatically, not in Linux:

https://www.digitalocean.com/community/ ... ux-servers

Matthew Moore video: https://youtu.be/xlTgaWs9BD0

My video: https://vimeo.com/110085401

You will also need to turn off Fast Boot in the BIOS otherwise it will always boot to Windows 10 and nothing else. Also disable Windows Boot Manager in the BIOS.

Did you checked your bios settings? Maybe windows bootloader is on the first place. If so change it.