Before such experiments it is always good to keep original copies of all VM files. My idea was to resize the base and all snapshot images and then fiddle with either Windows Disk Management tool from within guest OS or with GParted tool from a live CD. How To Enlarge a Virtual Machine’s Disk in VirtualBox or VMware Virtualbox - How do I increase the hard disk size of the virtual machine? - Ask Ubuntu #10818 (modifyhd -resize should warn users about existing snapshots) – Oracle VM VirtualBox #13046 (modifyhd -resize should not be permitted when snapshots exist) – Oracle VM VirtualBox

#9103 (modifyvm -resize doesn't work with snapshots) – Oracle VM VirtualBox My initial research was telling me I'd need to discard snapshots as I'd be able only to increase disk size of the original (base/root) image only: I wanted to reuse them for some development but dev software & frameworks I needed to install are disk space hungry and I had to increase disk size. I have a Win 10 VM with couple of snapshots which I used for some software testing.