Too many times I've forgotten the exact commands on how to compact the virtual drives. Especially for windows, where the tool used, used to have a different name of the argument passed to it. Compacting the drive can save you lots of disc space (last time my drive went from 12GB to 5GB), and for a smaller lap top drive, that makes a big difference.
Windows Guest:
Download SDelete from SysInternals and then run
Linux Guest:
Here, we create a file that fills the entire empty space, and then deleting it:
Host:
Finally, you let VirtualBox compact the drive
That's it really! I hope I'll remember it a little better this time.
Further info:
Use “sdelete -z” when Shrinking a Windows Guest’s Virtual Hard Drive
How to Compact a VirtualBox Ubuntu Guest’s VDI file
