Problem with SATA drive in G5s

Hi,

A few months ago a friend successfully installed a second SATA drive
(160Gb) into his G5. This week he bought another SATA drive (400Gb) to
replace the 160 Gb drive, which he moved to become the second drive in
another G5 where again it worked perfectly. The 400Gb drive could not
be seen by his G5 and both System profiler and Disk utility report no
drive present, though the disk appears to be getting power because it
produces quite a bit of heat.

Before deciding to return the 400Gb drive as faulty, he decided to
double-check and replaced the (then-working) 160Gb drive in the second
G5 with the new 400Gb drive. The second G5 could not 'see' this disk
either. So, it seems pretty certain that the 400Gb drive was faulty...

Not a great problem, because he can return it to the supplier...

BUT
The real problem is that the 160Gb drive that was previously working in
both the G5s now cannot be 'seen' by either! It now appears to have
the same problem as the 400Gb drive.

My question is:
Could the faulty 400Gb drive have damaged the G5s in some way that
stops any other drive working in the second drive position? Could that
in turn have damaged the 160Gb disk? Is there any way to check this
apart from buying yet another new drive?

I thought he might be able to buy an external enclosure for his 160Gb
SATA drive, but all the enclosures for SATA drives seem to have SATA
(or eSATA?) interfaces with the computer, and he is not inclined to buy
an enclosure AND a SATA PCI card just to check to see if his 160Gb
drive has been damaged.

Any suggestions would be much appreciated!

(BTW - both 160 and 400Gb drives are Seagate barracudas and both G5s
are 2.5MHz duals running OSX 10.3.9)

Thanks!

Kit