Hyper-V virtual machine at 100% CPU inexlicably

In some cases, I've seen Hyper-V virtual machines run at 100% CPU usage.  I can't explain it - but the cause is Windows Update on the VM itself.  The fix is to disable the Windows Update service from automatic startup and stop the service.  This fixes the problem.  You'd need to install updates manually going forward.

Superfetch causes 100% disk usage on Windows 8 machines

I was working on a Samsung laptop with Windows 8.1 where the machine's performance was subpar and I found that Task Manager shows disk usage was 100% (CPU and memory usage were normal).  When I opened resource monitor, I didn't see any programs using any more disk than normal.  Mostly from this page:
http://www.tomshardware.com/answers/id-2045646/windows-100-disk-usage.html

I decided to disable superfetch, which worked for me.  Disk usage dropped to single digits and would rise to 100% if/when the superfetech service was re-enabled.