Windows will not restart if your Registry Hives are larger than 2GB
The Windows Registry is a directory that stores settings and options for the operating system for Microsoft Windows. It contains information and settings for all the hardware, operating system software, most non-operating system software, users, preferences of the PC, and so on. A Registry Hive is a logical group of keys, subkeys, and values in the registry that has a set of supporting files containing backups of its data and is located in the \system32, \winnt, etc locations. If you are running 64-bit Windows or Windows Server, and the size of your Windows Registry Hives are larger than 2 GB in size, your computer just will not restart. This is because the registry hives in the x64-based version of Windows have a 2 GB size limit, and if the size exceeds this limit, the system is unable to restart. Microsoft has confirmed that this is a problem and a known issue. If you are experiencing this particular issue, then you can download Hotfix 496812 via KB2978366. Once you have applied this hotfix, you may be required to restart your computer.
