This is a Windows 2000 Executive character-mode Stop message. It indicates an attempt to release a thread by a mutex non-owner.
If this is the first time you have restarted after installing additional hardware, remove the hardware and restart again. Check the Microsoft Hardware Compatibility List to verify that the hardware and its drivers are compatible with Windows 2000. For information about the hardware, contact the supplier. If you are installing Windows 2000 for the first time, check the Windows 2000 system requirements, including amount of RAM and disk space required to load the operating system. Also check the Hardware Compatibility List to verify that the system can run Windows 2000. If Windows 2000 is loaded and no new hardware has been installed, restart with recovery options set to create a dump file. If the message continues to appear, select the Last Known Good option when you restart. If there is no Last Known Good configuration, try using the Emergency Repair Disk. If you do not have an Emergency Repair Disk, contact your technical support group.