How Windows 10 achieves its compact footprint

"DriveSpace (initially known as DoubleSpace) is a disk compression utility supplied with MS-DOS starting from version 6.0. The purpose of DriveSpace is to increase the amount of data the user could store on disks, by transparently compressing and decompressing data on-the-fly. It is primarily intended for use with hard drives, but use for floppy disks is also supported.

Microsoft's decision to develop DoubleSpace and add it to MS-DOS was probably influenced by the fact that DOS-based operating systems from other manufacturers (IBM and Novell) had started including disk compression software in their products.[citation needed]

Instead of developing its own product from scratch, Microsoft licensed the technology for the DoubleDisk product developed by Vertisoft and adapted it to become DoubleSpace. For instance, the loading of the driver controlling the compression/decompression (DBLSPACE.BIN) became more deeply integrated into the operating system (being loaded even before the CONFIG.SYS file)."

https://en.wikipedia.org/wiki/DriveSpace

Windows 8 version (2014):

"WIMBoot can significantly reduce the amount of space used by Windows files. This helps you provide more free space to users, and helps you manufacture Windows on PCs with smaller drives."

https://technet.microsoft.com/en-us/library/dn594399.aspx

If this mean that you will be able to go to BestBuy, and do a recovery to a pure Windows 10, blotware-less, without any .iso but just following a few steps, it seems even more interesting than a compact footprint!

Factory reset without recovery media isn't going to work if your runtime files have been infected and such.

It helps the rest of us too!