OT Laptop HD question

[John Lawson]

Thanks in advance to all who might know the answer to this - I am looking 
for a precise, 'this is exactly what it is' type answer, not guesses or 
maybes or speculation...  ;}

   All three of the HDs in my previous and current laptops, a Toshiba 
420CDT, an IBM Thinkpad A21m, and this Dell Latitude - have exhibited a 
sporadic 'snapping' behavior that is quite energetic (and alarming!). 
There is some combination of Windows launched programs that results in, 
occasionally, a small amount of disk activity and then a very loud snap, 
or bang, that can sometimes be felt in the desk the machine is sitting on.

   The Thinkpad did this every day for four years running typically 12-14 
hours 5/6 days a week - the memory controller on the mobo finally died - I 
have that HD hooked up as an external drive to the Dell - it hasn't done 
it since, but it's still working.  The Dell HD does this also, and in fact 
has done it twice during the composition of this post, BTW.

   Does anyone on The List have a "definitive" explanation for this 
behavior?  I have the drives backed up and mirrored via a PCMCIA adapter, 
so it's no big deal if one crashes - it's just unnerving to have something 
as small and precise as a 40G Travelstar undergoing these 'events'....


   Thanks!

John