Installed on ad2 moved to ad0

[John Murphy]

Installing FreeBSD 4.7 release on an old Pentium 120 which doesn't boot
from CD and the floppy controller's kaput.  Did a minimal install on my
main PC where the HD was ad2 then moved it to the older one where it's
the only drive on the first controller ad0.

I get the following output at boot time:
ata1-slave: ATAPI identify retries exceeded
ad0: 602MB <ST3630A> [1224/16/63] at ata0-master PIO3
acd0: CDROM <ICD-1200AT> at ata1-master PIO3
mounting root from ufs:/dev/ad2s1a
Root mount failed: 6
...
mountroot>

I could boot fine if I typed ufs:/dev/ad0s1a
But I'd like it to attempt to mount root from ad0 automatically.
Also, after entering the above there's a quick message to say:
swapon: /dev/ad2s1b: Device not configured

I can't seem to find where it's set to ad2, I've looked in:
/boot/loader.conf (just says userconfig_script_load=3D"YES")

I added a line to /boot/loader.conf.local like:
currdev=3D"disk0s1a" and re-booted.

Now there's a long delay after 'Loading /boot/defaults/loader.conf'
and then 'Unable to load kernel: Aborted!'

Pressing space during the ten second countdown and then typing 'show'
at the ok prompt shows currdev set to disk0s1a but loaddev=3Ddisk1s1a

Tried setting it and unsetting it but it tells me 'operation not permitted'.

So the question is (at last) how can I make it boot so I can add
loaddev=3D"disk0s1a" to /boot/loader.conf.local and will anything else be
necessary?

Thanks again
John.