What runs your PC lives in its memory: Windows itself, the drivers for every part, and whatever state they're in. A full start builds all of that fresh: Windows loads its kernel from its files and starts every driver again.

Since Windows 8, Shut down does something quicker, and Microsoft turns it on by default: Fast Startup. It closes your apps and signs you out, but in Microsoft's words, "the kernel session is not closed, but it is hibernated": Windows saves its kernel memory, drivers included, to a file on the drive (hiberfil.sys) and loads it straight back next time. Whatever state it was in comes back with it.

Restart is different. Microsoft again: "The Fast Startup setting doesn't apply to Restart." A restart does a full boot, built fresh from the files.

So when your PC acts up, restart it, don't shut it down. It won't fix a broken file or failing hardware, but it does give Windows a fresh start.

The PC, the memory blocks and the buttons are our own simplified drawings, not Windows' screens.

What's the longest your PC has gone without a restart?

Sources: Microsoft Learn, Fast startup causes hibernation or shutdown to fail in Windows 10 or Windows 8.1 (KB 3211190, updated 2026); Microsoft Learn, Distinguishing Fast Startup from Wake-from-Hibernation (2025).
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