Your Windows 8 installation using VirtualBox gave below error,
Your PC needs to restart. Please hold down the power button. Error Code: 0x000000C4 Parameters: 0x0000000000000091 0x000000000000000F 0xFFFFF80038F4BA80 0x0000000000000000
Upgrade the VirtualBox to the latest (version 4.3.2 – during this article was published). We encountered this error in VirtualBox 4.2.3.