Shrink VirtualBox vdisks After Freeing Space (Windows guests)

Issue On dynamically allocated vdisks, freed space on a guest is never released back to the host once freed. Cause This is by design. Resolution The procedure for shrinking (compacting in VirtualBox parlance) is straightforward and consists of a series of steps. Delete files on the guest to achieve the desired amount of free space Zero free space out with an appropriate utility Shut down guest Compact disk Zeroing guest free space is simple: Microsoft provides an excellent utility through its Sysinternals group called SDelete. »