I remember seeing a thread a while ago with possibly similar problems, but can't at the moment locate it. Basically if I leave the machine 'idle' for a while, so the Mac has gone to sleep, and then return, sometimes I'm seeing strange display behaviour from the virtual machine. W10. Two versions (W32 Anniversary and W64 Creators). I'm running an i7 27" 2017 iMac 32GB/3TB (fusion). Retina display. Second screen is a Dell Ultrasharp 25" on the displayport. I'm running the Windows on this. Parallels 'sees' that I have a Retina main display, and defaults to setting the resolution to 5120*2804 (running a window to fill the screen, but not running 'full screen'). The monitor though is only 2560*1440. So Parallels is getting confused about the actual resolution available (though things display correctly).... Real problem though, comes when the Mac sleeps. Fault seems to be worse the more windows that are open on the Windows desktop. After the return things redraw very slowly, and depending where the cursor is. So if you open the explorer window for example, it comes up 'empty', and if you then move the cursor across it, parts are displayed as the cursor crosses the window. Reboot, and it's OK again till the next sleep. Now if I change the Parallels settings and turn off '3D acceleration' completely, it does not happen. WDDM driver loads, screen performance is less good, but works fine. If I select DX9, W10 disables the Parallels WDDM driver, and still works OK. If I select DX10, the WDDM driver loads OK, but the problem appears. Performance though is better till the problem appears. Suspect trying to handle this massive (non existent...) resolution is causing the problem. Suggestions?.