virtualbox.org

Windows 10 Preview worked fine on VBox... until I upgraded to the latest version of VBox (4.3.30).
My host system is 8.1.
I have created a VM called Windows 10, selected Windows 10 (64-bit) from the drop-down menu (I even tried Windows 8.1 64-bit).
I made sure nesting and hardware acceleration was enabled.
I set the Storage as the .iso on my hard drive, booted up, and then a Blue Screen:

The digital signature for the file could not be verified:
c:\windows\system32\boot\winload
Error code 0x0000428

Try the latest VirtualBox5 5.0.2, it has the best support for Windows 10. Windows 10 support is still an ongoing effort.

You should also try the latest test build 5.0.3-102224

Unfortunately, this didn't make any difference!