Now that we know future updates to Windows 10 will reserve 7 GB of space on our hard drives, there is a way to stop this from happening. While the reserved storage issue is currently only available to Windows Insiders on the Fast Ring, a public rollout might be on the way with Windows 10 version 1903, coming this Spring. The problem with this is, not everyone has 7 GB of space to spare, and that space could be used for much more important things, like your files.
For Windows Insiders on the Fast Ring looking to completely disable the 7 GB reserved storage that Microsoft plans to hold back for future Windows 10 updates, here's what you need to do, as noted by wccftech.com. This is basically the opposite of the instructions in the Quest Insiders need to complete to get reserved storage to work in the first place. But if you can turn it on in the Registry, you can turn it off!
- Hold down the Windows Key + R to open the Run Prompt. Type "regedit" (Registry Editor). Press Enter. Click Yes to the UAC (User Account Control) to enable administrator editing privileges. Alternatively, you can also type regedit.exe in the Start menu and choose "Run as administrator."
- Once you are in Registry Editor, go to the following directory: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ReserveManager
- Go to ShippedWithReserves as indicated. Double click ShippedWithReserves and change the hexadecimal value from 1 to 0.
Restart your Windows 10 PC for the changes to take effect. If you want to test to see if your registry changes were successful. Go to Settings > Storage settings > Show more categories > System and Reserved > Reserved Storage. Note that messing in the Registry can do damage to your computer, and also note that reserved storage is a work in progress, and all of this, including if it's included at all in shipping versions of Windows, is uncertain at this time.