The procedure is the following:
*Install Windows Service Pack 1 then ...
*Start and elevated command prompt (run 'CMD' as administrator) and ...
*Run the DISM command, which replaces the old VSP1CLN and COMPCLN we used on previous Windows versions: DISM.exe /online /Cleanup-Image /spsuperseded
*Wait 10 minutes before the task completes (it ends with "Service Pack Cleanup operation completed. The operation completed successfully")
Normally you should have been able to reduce the Winsxs folder size by 1 or maybe 2 GBs, sometimes more. Saved space may vary a lot.
DISM.exe /online /Cleanup-Image /StartComponentCleanup
The following command will remove all old versions of every component. You won’t be able to uninstall any currently installed service packs or updates after this completes:
DISM.exe /online /Cleanup-Image /StartComponentCleanup /ResetBase