I had a screeching MK4004GAH (HDD1524) 40.0GB 1.8-inch HDD.
for ipod classic 4g
I know that any dust is very bad and it destroys hard drives. But as I was only going to throw the hdd away. i thought what the @@&^.
Opened it up moved the arm with the tip if a screwdriver a couple of times also I pushed the top of the metal case out slightly with my thumb.
then screwed it back together
( if the cover of the hdd has been bent in slightly another method could be too use a strong sticky tab on the outside of the case and pull it outwards I'm thinking of the type used on self affixing door hooks etc. I think that one reason for this hdd not working was that pressure had been put on the thin metal top casing bending the cover in slightly and affecting the hdd somehow )
If I was to try this again I would go about making a temporary clean space by wearing latex gloves as mentioned in an earlier post.
and working with the hdd inside an unused medium sized clear ziplock bag.
The hdd is working now. ( but for how long! only time will tell )
certainly long enough to recover some data.