It sounds more sinister than a power problem, I ran an 030 & HD off a standard A1200 psu for years without a problem...
What I'd do is open up my stepdad's laptop and swap drives, and see what happens :-) or put it in another Miggy?
Also some IDE cables are modified so that not all the pins are connected. I can't remember whether or not 2.5" IDE cables are keyed or not, but if the cable's the wrong way round that could be a contributing factor... :-)
