Phead's answer is right for older SCSI cards but most modern controllers support the Multi() option.
The layout of the BOOT.INI file is as follows:
[boot loader]
timeout=1
default=multi(0)disk(0)rdisk(0)partition(1)\WINNT
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINNT="P1 Windows 2k Server"
multi(0)disk(0)rdisk(0)partition(2)\WINNT="P2 Windows 2k Server BACKUP"
The timeout setting is set to just 1 second, this allows the system to boot quickly and enables it to be caught if the backup operating system is required. The default setting is set to the operating system to be loaded if a selection has not been made within the timeout of 1 second. The [Operating Systems] section lists the operating systems configured on the PC. In this case the user will be given a menu of "P1 Windows 2k Server" located on Partition 1 or "P2 Windows 2k Server BACKUP" located on Partition 2.
Your will need to make sure that both partitions have the updated BOOT.INI
It is a very good idea to create a NTx Emergency Boot floppy, format a diskette under Windows NT so that the NT boot sector is copied to the diskette, then copy the following files to the floppy from your NT hard disk.
1.BOOT.INI
2.NTLDR
3.NTDETECT.COM
4.NTBOOTDD.SYS.SCSI
5.KERNEL32.DLL
You only need 1,2 & 3 to boot an IDE PC, Number 4 is your specific SCSI driver and number 5 is useful to have to hand as it is a target for people wishing to cripple your server.
You will need to edit the BOOT.INI file on the floppy disk so that it can boot from any partition, here is an example of a BOOT.INI that waits 10 seconds for you to make a choice, it then defaults to partition 1, if that fails the you can reboot and choose each partition in succession. If none boot, check that there are actual NT partitions and that none of them are hidden.
[boot loader]
timeout=10
default=multi(0)disk(0)rdisk(0)partition(1)\WINNT
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINNT="P1 Emergency boot on Partition1"
multi(0)disk(0)rdisk(0)partition(2)\WINNT="P2 Emergency boot on Partition2"
multi(0)disk(0)rdisk(0)partition(3)\WINNT="P3 Emergency boot on Partition3"
multi(0)disk(0)rdisk(0)partition(4)\WINNT="P4 Emergency boot on Partition4"
multi(0)disk(0)rdisk(0)partition(5)\WINNT="P5 Emergency boot on Partition5"
multi(0)disk(0)rdisk(0)partition(6)\WINNT="P6 Emergency boot on Partition6"
The multi(0)disk(0)rdisk(0)partition options allow for the selection of disks on different hard disk controllers, but most modern controllers work with the above settings.
Hope this helps
AJ