Microsoft today provided a lengthy explanation of two related and key new features called PC Reset and PC Refresh. The post on Building Windows 8 goes into quite a bit of detail, expanding greatly on the information I provided previously in my Windows 8 Developer Preview overview. There, I wrote:
PC recovery. The Windows 8 recovery stuff is awesome and is going to represent a major milestone in PC reliability. There are two major options to note, PC Refresh and PC Reset. With Reset, you get a full reset, and the entire PC is wiped out and reinstalled from scratch. This process takes a few minutes currently and will return the PC to its factory condition; it doesn't require any external discs or USB key. With Refresh, your files, data, favorites, personalization, and metro style apps are all backed up, the OS is wiped out and replaced, and then everything is reapplied to the PC, leaving you with a pristine, running copy of Windows with everything (except for classic applications) exactly the way they were before. It currently takes 4 to 5 minutes.
I also previously published a Windows 8 Refresh Your PC Screenshot Gallery that features numerous screenshots of these features in action.
But back to Microsoft.
According to the post, PC Reset and PC Refresh will go a long ways towards making Windows 8-based PCs behave more like devices, since these features are akin to a hardware "reset" button. The two features are differentiated as follows:
Reset your PC. Remove all personal data, apps, and settings from the PC, and reinstall Windows.
Refresh your PC. Keep all personal data, Metro style apps, and important settings from the PC, and reinstall Windows.
What's most amazing about these features, of course, is how fast they are. And while I've experienced this in the real world, let's just use the post's own numbers: On the Developer Preview version of Windows 8, PC Refresh takes about 8 minutes and 22 seconds, while PC Reset (thorough, with BitLocker) takes under 6 and a half minutes. (Without BitLocker enabled, it's more time-consuming at almost 24 minutes.) The same type of restore using a system image takes about 24.5 minutes by comparison.
Anyway, the post has a lot more detail, as always, if you're morbidly curious. Plus, there's a video in there as well.