Hello, Ronny. Please stop the virtual machine by navigating to Actions -> Stop from the virtual machine menu on the upper left of your Mac screen, optimize the virtual machine's performance by following the steps in http://kb.parallels.com/112091 under 'Virtual Machine Configuration', disable '3D Acceleration' and 'Vertical Synchronization' in the same window under Hardware -> Graphics -> Advanced Options and then restart Windows. Let us know how it goes.
