If he does not have a FAT16 boot partition, then this will work not until a service pack (4). Most undoubtedly, his Win2k drive is FAT32 or NTFS 5.0, and NT cannot read from either of these for boot.
What about drive letters? Win2k will not allow itself to be pushed from C: to D: because it is the boot device. NT will believe that it, too, is the boot device, as the other drive was not plugged in. What happens, should you get to boot into NT, and it believes that it is the boot drive when Win2k wants to demote it to the D: drive?
He should get a STOP command with INACCESSIBLE_BOOT_DEVICE when he adds multi(0)disk(0)rdisk(1)partition(1) to his boot.ini because the file system difference stops it.
You should have seen the post I wrote before. It was just like yours with details on boot.ini and everything...but I figured I would just put a link.
The easiest thing to do would be to get Partition Magic 6.0, resize his Win2k drive by 2MB, make a FAT16 partition at the beginning of the drive, boot with the 2000CD, choose to repair the installation (it will fix the boot sector), and then try to get his NT working. Since he didn't go NT --> 2000, he will have a harder time.
good luck