JSI Tip 0611 - Your system hangs during heavy I/O and you can only restart.

There is a bug in NT 4.0 that causes the system to stop responding during very heavy I/O operations such as multiple file copies. You have to reboot.

Microsoft has confirmed the above is a problem and no fix has yet been found. If the problem is pervasive, consider setting UtilizeNTCaching to 0 until a hotfix is available. See tip 231.