If you run Windows 2000 on a hard disk and replace the mainboard of the PC afterwards, Windows may abort booting displaying "INACCESSIBLE BOOT DEVICE," because Windows 2000/XP only installs the IDE-drivers that are needed for the very first installation. To make the hard disk boot under the new mainboard, system files and registry entries need to be added. The use of the following file is very helpful, but installation is done at your own risk:
Windows 2000/XP fix für "INACCESSIBLE BOOT DEVICE"