Malfunctioning Drive Controller on ASUS A7V8X?

Hi.

I am having very strange issues with my hard drives since a SATA drive
failed. Old PATA drive has slowed down to 2 Mb/s transfer rates, new SATA
drive beeps every 0.5 s or so and does not get recognised. Please see
below for details.

Could my failing drive have damaged the motherboard in some weird way? Or
is the motherboard killing all my drives? I'd appreciate any suggestions.

My Spec
=======

ASUS A7V8X motherboard/Athlon XP 2000+
(Promise 376 SATA controller on board)
(Old) PATA33 Maxtor 53073U6 30 Gb
(New) SATA Seagate Barracude 7200.7 120 Gb
Win XP Pro

History
=======

Bought new SATA drive in Jan and moved system partition there. Everything
was fine until mid-June, when SATA drive first failed to be recognised on
first cold boot and then failed completely: BIOS would recognise
something was connected to the SATA port, but would give up on "Searching
for IDE Device" after a minute or so, and boot off the PATA drive.

SATA drive also failed to work in another machine, so was sent back for
replacement under warranty. It didn't seem to be a head crash, just a
failure of the controller.

Situation Now
=============

Started using PATA drive as my main system drive: it is VERY slow.
Diskbench reports that a filecopy of a 700 Mb CD image is performed at a
rate of 2 Mb/s! Windows takes about 5 minutes to boot. Apart from that,
things more or less work.

SATA drive arrived back. At first, seemed to be detected OK and I was
able to copy the system partition back onto it from a backup. Then,
within a few reboots it started failing: it would be recognised, Windows
would start booting, the drive would stop about 3 or 4 seconds into the
boot sequence, beep and the computer would reset, back into the BIOS.

When I tried booting from the PATA drive instead, with the SATA
connected, it would go OK, but then, whenever I tried accessing the SATA
drive, the drive would whirr up, beep, the just-opened window would come
up with "Not Responding". After 30-60 seconds this would get resolved and
the directory structure would appear. If I tried accessing it again, the
same would occur.

Now, when the SATA drive is connected to either of the controller ports,
it starts beeping every 0.5s immediately on switching on the power, while
the controller BIOS is loaded, but fails to find a drive after searching
for 60 secs or so, i.e. same symptoms as with the first, dead, SATA drive
(apart from the fact that the original did not beep).