Originally Posted by
BOAC
Thought I should 'report back' - problem solved (I think!). Due to frequent plugging and unplugging of my failing ***** Maxtor drives I reckon the female connectors on the power lead had slackened off. A quick poke with a small screwdriver to reclose them and I then plugged that connector onto my DVDRom which was not being replaced 'under repair warranty' every 5 minutes like the drives and all well so far.
Thanks - I'd been wondering if you got it sorted.
Just a thought: if you'd gone Keef's route and replaced the power supply, that would have cured it, too,
and you would never have discovered what the real problem was. 
Complicated things, these 'puters, ain't they?
p.s. Nothing wrong with Keef's suggestion, of course, 'twould have worked, and psus are also inexpensive these days.