Have you ever been using your computer and your system suddenly stops responding in ways like it if you try to open something it just hangs? One time I tried deleting a folder and it said it was in use, but it really wasn't. If this ever happens to you, you can follow these simple steps to 'reboot' your computer without 'rebooting' it.

Press CRTL + ALT + DEL

Goto the 'processes' tab and click explorer.exe once and then click 'end process'.

Now, click File > New Task and type explorer.exe

Everything should be fine now!
If the problem is major, I would recommend actually shutting down then starting up again.