This worked successfully for me for installing Android x86 4.4-r5 (android-x86-4.4-r5.iso) on VirtualBox 5.2.0:

Create a VM: Select Type as Linux and Version as Linux 2.6 / 3.x / 4.x (32-bit) and click Next

Leave memory the default of 512 MB (or choose more, doesn't matter)

Create a new virtual hard disk. I chose 8 GB

Click Start

In the popup select the iso: android-x86-4.4-r5.iso

In boot menu select Installation - Install Android-x86 to harddisk

In Choose Partition menu select Create/Modify partitions

In Do you want to use GPT question select No

cfdisk program will open

Select New and select Primary as partition type, set size to 100 MB and select Beginning

Select bootable. Now the Flags column should say Boot for the new paritition

Select the free space and select New and select Primary as partition type, leave size as default to fill the remaining free space

Select Write and type yes and press Enter

Select Quit

Now the Choose partition menu should display this configuration:

sda1 unknown VBOX HARDDISK

sda2 unknown VBOX HARDDISK

Select the second partition: sda2 and select OK

Select ext2

Select Yes in lose data warning popup

Wait for formatting to finish

In Do you want to install boot loader GRUB? question select Yes

In Do you want to install EFI GRUB2? question select Yes

In Do you want to format the boot partition /dev/sda1? select Yes

In Do you want to install /system directory as read-write select Yes (doesn't matter for us)

Wait for installation to finish

In Congratulations! menu select Reboot

Remove the installation iso so it doesn't boot back to installation

I just spent 3 hours trying to get this to work. Hope this helps someone.

Bonus 1:

To set up ADB debugging see http://www.android-x86.org/documents/debug-howto :

Enable Developer options in Android and enable USB Debugging

In VirtualBox go to Devices -> Network -> Network Settings

Make sure Adapter 1 tab is selected and click Advanced

Make sure Cable Connected box is checked

Click Port Forwarding

Click the plus sign

Set the following values: Name: adb, Prodocol: TCP, Host IP: leave blank or set to 127.0.0.1 to make it accessible from localhost only, Host Port: 5555, Guest IP: leave blank, Guest Port: 5555.

Click OK

To connect via ADB:

# adb connect localhost:5555

Now adb devices should show:

List of devices attached

localhost:5555 device

Bonus 2:

In VirtualBox Input menu unselect the Mouse Integration and now mouse pointer will show up!