RH 7.2 boot problem

["Chiu, PCM (Peter) " <P C M Chiu rl ac uk>]

We have an Intel PC with 2xPentium 2 450MHz cpus currently
running RH 7.1 on one of the SCSI disks (sdb1). 

I added in a Maxtor 160GB disk and a DVD on the IDE primary bus.
The secondary IDE bus is connected with a Toshiba CD-R drive.

A Yamaha CD-WR is also connected to a separate SCSI bus (sdc).

I mounted a new RH 7.2 on a second SCSI disk (sda1) using 2 partitions:
(sda1: as / and sda2: as swap) and specified the following:
a. use GRUB, 
b. install boot record on /dev/sda1, first sectior of boot partition, and
c. default boot disk being /dev/sda1.

The installation appears to complete okay with no error.
But when it boots up, it complained missing operating system.
No GRUB window is displayed.

I rebooted the system, now using the rescue floppy built durning
the installation, but got the same error.

I can still boot up the old 7.1 system on sdb1, and checked 
the grub.conf on /dev/sda1, but nothing seems unusal.
I can see the new Maxtor as hda, and the dvd as hdb.

Any idea where it might gone wrong?  It appears to me the
installation procedure fails to set the boot record onto the
SCSI disk sda1.  Is it because of the presence of the hda?