As todays devices often got small SSD drives, it is more important than ever to free up unused space to extend the live of your SSD drive and also to make room for other goodies.
Windows stores old update files and previous versions of windows in case you want to revert to the old version and uninstall it.
But after many months there is certainly no need on all devices to be able to go back to old Windows editions…

There is a way to clean up that space and im talking about 5-30GB of space, depending on your update behavior…
Just open a cmd commandline with admin rights and enter this command:
On modern Windows versions like windows 8, windows 8.1, windows 10, enter:
dism /online /cleanup-image /startcomponentcleanup /resetbase

On old windows 7, enter:
dism /online /cleanup-image /spsiperseded

And remember to always keep an update if you try out new things.
Enjoy your new space!