My boot.ini should be changed because I installed a second hard drive and mirrored the C:. The help-file says I should have seen a message with the new ARC Path after mirroring but I missed that ...
Boot.ini is now:
multi(0)disk(0)rdisk(0)partition(1)\WINNT="Microsoft Windows 2000 Advanced Server" /fastdetect
the mirror is on Disk 1
disks are identical, SATA