Derived from these instructions on HowToGeek

In this tutorial we assume a linux host and a windows guest

1. Clean up files

2. delete winsxs: https://helpdeskgeek.com/windows-11/what-is-the-winsxs-folder-why-is-it-huge-and-how-to-cleanup/

3. Clean up system files (search for “cleanup” in start menu)

4. Turn off hibernate

   powercfg.exe -h off
   

5. Turn off page file

6. Turn off system restore

   https://www.howtogeek.com/5482/make-system-restore-use-less-space-in-windows-7/

7. find and delete shadow copies and backups: https://superuser.com/questions/1746099/system-volume-information-folder-huge

   • https://www.thewindowsclub.com/delete-volume-shadow-copies-in-windows

8. limit size for shadow copies: vssadmin Resize ShadowStorage /For=C: /On=C: /MaxSize=320MB

9. delete winreaagent folder: https://www.majorgeeks.com/content/page/what_is_the_winreagent_folder_and_can_i_delete_it.html

10. defrag hard drive

    defrag c: /U /V
    

    https://www.partitionwizard.com/clone-disk/optimization-not-available.html

11. write zeros to hard drive

    .\sdelete.exe c: -z   
    

    • sdelete utility
    • Instructions from HowToGeek

12. Find the virtual hard drive you want to shrink. In the host OS, type:

    VBoxManage list hdds
    

13. Execute the shrink command

    VBoxManage modifymedium disk "/path/to/disk" --compact