Usually if you see this happen, its time to reinstall windows
Uhh, no. That wouldn't be very useful. The mixed-up icons are totally useless, and reinstalling Windows would fix them as much as rebooting would.
In any case, this is a bug with Windows, and usually not one that means anything, except perhaps that you have too many files in one folder (especially ones with different icons). In any case there's not really a lot you can do to fix it, but it
is totally harmless.