The Windows 2000 CD is bootable. Insert that CD, reboot, and then the Windows 2000 setup will start. Once in there, do a repair, it should find that Windows 2000 is installed, and offer to repair the files needed for booting (boot.ini, and maybe others). Note, you may need to move the CD rom up in the motherboard's bios for the order that it boots from. IE: A:, CDROM, C: