How to Resize VirtualBox Disk Image in Windows

The procedure to resize or expand VirtualBox disk image (VDI) in Windows will take the following steps:

1. Backup your VDI disk image
2. Run elevated privilege Command Prompt
3. Change the directory to where your VirtualBox is installed. It usually located on C:\Program Files\Oracle\VirtualBox\
4. Run this command, VboxManage.exe modifyhd "YOUR_HARD_DISK.vdi" --resize SIZE_IN_MB

Example: C:\Program Files\Oracle\VirtualBox\VboxManage.exe modifyhd "C:\Users\Vootwerk\VirtualBox VMs\Windows 8 Enterprise\Windows 8 Enterprise.vdi" --resize 40960

5. Once VDI disk image is resize, you will then need to extend the partition on your Windows VM to use the newly unallocated disk space.