To dual boot Pop!_OS alongside another OS, use the “Customize Partitions…” option when selecting a drive.
If you already have an available partition that you want to erase and replace with Pop!_OS, skip to the next section.
If you don’t have an available partition, you can create one using the “Modify Partitions…” button to open GParted.
First, make sure you Select the correct drive in the top-right of GParted.
Right-click the desired partition and select “Resize/Move”. Resize the partition down to make room for a Pop!_OS partition, then select the “Resize/Move” button.
Right-click the new “unallocated” space and select “New”. Choose the filesystem you want (if unsure, keep the default ext4), then select the “Add” button.
When you’re ready, select the “Apply All Operations” icon at the end of the toolbar. Once the process is complete, close the GParted window and the installer will update with your changes.
Select the partition on which you want to install Pop!_OS. Choose “Use partition” and select “Use as Root (/)”. On EFI installs, you must also choose a Boot (/boot/efi) partition. One should exist from your other OS; choose it, and do not format it.
Once you have your partition(s) selected, select the red “Erase and Install” button. This will apply your changes and begin the installation. When you restart your device after installing, it should automatically boot into Pop!_OS where you can set up your user. Note that on BIOS installs, the Pop!_OS entry may read “Ubuntu”. To boot your other OS:
Choose your previous OS with the arrow keys, then press Enter.
Windows 8 and later uses a “Fast Startup” setting which prevents Windows from fully shutting down and allowing other OSes to use the disk. Before you can properly dual boot with Windows, you must disable this setting in Windows.
In your Windows install, open Control Panel and head to “Power Options” Select “Choose what the power buttons do”, select “Change settings that are currently unavailable”, then disable the “fast startup” setting. Note that Windows updates may occasionally turn this setting back on without asking, so if you are unable to boot into Pop!_OS, check this setting first.