System and reserved files use 70GB. How delete them?

@TairikuOkami ok, will try out those commands as well, thanks! Yes I've been using CCleaner for some time now, and certainly as soon as I started using my current laptop. It usually only cleans between 1-2.5GB at a time. Perhaps I need to select more compartments for it to clean? But as I said, I worried about it cleaning essential things and causing any harm.

TairikuOkami said:

...it is unlikely anyone would do it anyway, unless some serious issues were caused by an update.

I agree, but it's worth mentioning the 'health warning' so one can make an informed choice of whether or not to use /ResetBase.

lemonteajunkie ... You might want to check and clean up the Storage Volume Shadow Copies in Device Manager.
Open Device Manager / View / Show Hidden Devices
Expand Storage Volume Shadow Copies ... if you have any greyed out Generic Volume Shadow Copy, just right click on each of the greyed out ones and uninstall.

Note: This doesn't help regain any HDD space, just good practice IMO when deleting/cleaning up restore points.

@Eagle51 thanks, have done as you suggested. Only one greyed out entry at the time.