I know it's not quite the same thing but on the small mechanical parts
of hydraulic systems I work on, I find that some of them are almost
impossible to get sorted out unless you dunk them in a bucket of petrol
for a while and flush the worst of the crap out before you even *start*
to take them to bits.
Completely OT, but when you dismantle a Citroen hydraulic system, you do
clean round the unions (unleaded petrol is the recomended cleaner in the
factory workshop manual..) before undoing things, to prevent said dirt
ending up inside the sytem.
However, any antique clock repairer will tell you not to clean a clock
before dismantling and inspecting it. Often marks in the dirt will give
information as to the size of a missing part, of what's been rubbing
where it shouldn't and so on.
In the case of computers, I think the latter applies. They're unlikely to
be as dirty as the underside of a car :-). And as with clocks, a mark in
the dirt may show where a linkage has been scraping on the chassis or
something.
-tony