I recently wrote two blogs about preventing Windows 10 from installing bug fixes. The first one, Defending against Windows 10 bug fixes, included a couple very much out of the box solutions.

One of these wild ideas derived from my experience owning a Windows 10 laptop which shipped with a measly 32 gigabytes of storage. Of course, that number is inflated, the actual available storage space is 28.5 GB, and, with almost no apps installed and lots of tweaks to save space, it now has 7.9GB of free space on the C disk. Needless to say, the first time Windows 10 tried to update to a new Service Pack, it failed due to the lack of storage space. I eventually had to do a clean install to upgrade to a newer Service Pack.

Thus, my out-of-the-box suggestion for blocking Windows updates: leave very little free space on the C disk.

According to Microsoft, installing a Service Pack (they call it a Feature Update) typically requires 6 to 11GB of free space. Monthly bug fixes (their term is Quality Updates) require roughly 2 to 3GB. So, by choosing the amount of free space on the C disk you can allow or throttle monthly bug fixes and Service Pack upgrades.

This may especially come in handy for Home Edition users who have far fewer choices for delaying bug fixes and Service Packs.

Perhaps the easiest way to consume mass quantities of space on the C disk is to assign it to the page file. To do so, first see how much free space there currently is on the C disk and decide how much you want to leave. Then, check the current size of the page file by looking at the properties of the pagefile.sys file in the root of the C disk. Finally, calculate what the new size of the paging file needs to be to leave the desired free space. All these calculations will be in gigabytes (GB) however Windows 10 sets the page file size in megabytes (MB). One GB is a thousand MB. For example, 9.5 GB is 9,500 MB. You may need to restart Windows, so pick an appropriate time, just in case.

The steps to change the page file size are:

1. Control Panel -> System
2. Advanced system settings (in left side column)
3. If you are not logged on as an Administrator, you will need to provide an Admin password
4. There are Settings buttons in this window, click on the one in the Performance section
5. Go to the Advanced tab
6. Click on the Change... button
7. Turn off the "Automatically manage paging file size for all drives" checkbox
8. Click on the Custom size radio button
9. Finally, we get to set the size of the page file. Make the initial size and maximum size the same. Again, the size is set in MB, not GB.
10. Click on the Set button
11. OK, OK, OK, OK, etc.

This trick, however, won't last. Microsoft is working on a new feature that insures sufficient hard disk space for Windows Update on Windows 10. Perhaps someone there read my blog?

The new feature, called "Reserved Storage" will be introduced in the upcoming 1903 Service Pack for Windows 10. It will reserve roughly 7GB of disk space for use by the system. The feature will be enabled automatically on new devices that ship with Service Pack 1903 pre-installed and will also be enabled when 1903 is cleanly installed. Existing copies of Windows 10 will not have the feature enabled when they upgrade to 1903.

For more about Reserved Storage see Windows 10 reserved storage explained by Martin Brinkmann (January 8, 2019) and Windows 10 and reserved storage by Jesse Rajwan of Microsoft (January 7, 2019).