Windows is especially effective at compressing files and folders to reduce the space they occupy on your hard drive—which is ironic, considering the fact that hard drives these days have enough capacity to stretch to Steve Ballmer’s house and back three times.
Even so, compressing files and folders can occasionally be useful, especially when hard drive space is running short, or when you want to email files to someone without dooming them to an all-night waiting session. Maybe that’s why Microsoft has endowed Windows with two different schemes for compressing files and folders: NTFS compression and zipped folders.
Windows 8.1, since you asked, requires a hard drive that’s formatted using a software scheme called NTFS. It’s a much more modern formatting scheme than its predecessor, something called Fat 32—and among its virtues is, you guessed it, NTFS compression.
This compression scheme is especially likable because it’s completely invisible. Windows automatically compresses and decompresses your files, almost instantaneously. At some point, you may even forget you’ve turned it on. Consider:
Whenever you open a compressed file, Windows quickly and invisibly expands it to its original form so you can edit it. When you close the file again, Windows instantly recompresses it.
If you send compressed files (via disk or email, for example) to a PC whose hard drive doesn’t use NTFS formatting, Windows once again decompresses them, quickly and invisibly. ...