Introduction
I have received a number of comments with regards to the procedure for dual booting Windows 10 and Ubuntu.
Some people have noticed that the free disk space they created is not available for use when they try and install Ubuntu.
This article aims to explain why you wouldn't be able to use the free space and who will be affected by this.
Who Is Affected?
If your computer uses the Unified Extensible Firmware Interface (UEFI) then you will not be affected. If however your computer has a legacy BIOS then you may be affected but only if your computer's hard drive already has 4 primary partitions.
How To Check Whether Your Computer Is Using UEFI Or A Legacy BIOS
As we are going to be using the Disk Management screen anyway the easiest way to check whether your computer is UEFI based or not is to right click on the start button and choose the "Disk Management" option from the menu.
Look at the partitions for your hard disk (which will probably be disk 0). If you see a partition called "EFI System Partition" then you can feel very smug and stop reading this article because you will not be affected by the issue.
The Issue Explained
If there is no EFI partition then you could have issues with partitioning when installing Ubuntu.
The older style BIOS only allows a user to create 4 primary partitions on a disk whereas the newer GPT partitioning system allows more than you will ever need.
The problem with having just 4 partitions available is that Windows 10 often takes up a number of partitions itself. There is one for Windows and at least one for a recovery partition. The manufacturer of the computer quite often has a partition for its own recovery partition and then another partition may have been created for another reason.
As there can only be 4 primary partitions if you have shrunk the Windows partition the free space you have created cannot be placed in a partition and therefore cannot be used.
When you try to install Ubuntu you will not see an option to install alongside Windows and when you choose something else as an option you will see unusable space as shown below.
The Solution
I can't give you a step by step solution to fix this as it depends entirely on what partitions are currently used on your system.
I can however tell you that all is not lost.
Whilst you can only have 4 primary partitions you can split a single partition into a number of extended partitions. If you can free up one of the 4 primary partitions you can then create a number of logical/extended partitions on that single partition for installing Ubuntu.
How To Remove A Partition
Freeing up a single partition is the difficult bit.
If you have shrunk the Windows partition to free up space then you will want to delete the partition next to it (no, not the Windows one, probably the one to the right).
The issue is however, what are those partitions used for. If the partition is a Windows recovery partition then you could elect to move that partition to an external hard drive.
The partition might also be the recovery partition created by your computer's manufacturer. In this case you should find the software used by the manufacturer as this may allow you to backup the system to an external hard drive or USB drive which means you can delete the manufacturer's recovery partition and use it with the free space you created by shrinking Windows.
Another option is of course to use Macrium Reflect which I recommended as the backup tool as part of the process for dual booting Ubuntu and Windows 10. (Click here for that guide). You can use Macrium to create recovery media on DVDs, USB drives and external hard drives. With the recovery media safely stored externally you can safely delete the Windows recovery and manufacturer's recovery media.
If you have another partition called data then you might wish to move the data from there onto the Windows partition or indeed another drive such as an external hard drive and delete that partition.
You can delete a partition within the disk management tool by right clicking on it and choosing "delete volume".
Windows recovery partitions cannot be deleted using the disk management tool because the partition will be protected. This guide shows how to delete a protected partition.
It may be the case that the manufacturer's partition or Windows recovery partition is quite large and therefore you don't need the free space created by shrinking Windows any more. You can give the disk space you gained from shrinking Windows back to Windows by right clicking on the Windows partition in the disk management tool and choosing "Extend Volume".
Given the choice between removing the Windows recovery partition and the manufacturers recovery partition I recommend removing the manufacturer's partition. I would however make sure that I had a viable recovery option available via Macrium reflect or another such tool.
The upshot is that you want to get to a position where you have only 3 primary partitions and then a section of free space on your computer large enough to install Ubuntu.
You should now be able to follow my guide to installing Ubuntu alongside Windows 10 to complete the task.
Summary
This only affects people who are using a computer with a legacy BIOS that already has 4 primary partitions in use.
To fix the issue remove one of the 4 primary partitions.
Important: If you decide to remove a data partition make sure you have backed up the data first. If you decide to remove a recovery partition make sure you have created other recovery media
After deleting one of the 4 partitions you should be left with 3 primary partitions and an area of unallocated disk space.
When you run the Ubuntu installer you should now see the option to install alongside Windows 10.
If you do not get the option to install alongside Windows 10, choose the something else option as the installation type and create 2 extended partitions in the area of free space, the first taking up most of the disk space and mounted to root (/) and the second taking up around 8 gigabytes for swap space. The amount of swap space can be reduced or increased depending on the age of your machine and amount of memory available.
