Optimize disk usage in virtual Windows

Dynamically expanding virtual hard disks tend to become bloated, but it is possible to shrink them.

1. Download the SDelete utility. Save it on C:\ for simplicity’s sake.

2. Run

sdelete -c C:

in command prompt on your guest Windows (I still use Windows XP, Vista or 7 may be different in that regard). That command marks all unused clusters on C:\ as free.

3. Shut down your guest machine and run the following command in terminal on your host:

VBoxManage modifyvdi /media/share/virtualbox/1C.vdi compact

Thanks to Ivan Femia for that trick.