I just finished loading Mint plus everything to an 80-gig hd, in a spare old Compaq presario... When I returned after adding 2-gigs of music the screen is bouncing vertical about 1/64th of an inch, at about 30-hertz... That could drive someone to "bolt, and run out in the street naked, screaming excerpts of political dogma"...
Changing the screen freq to 75-htz stopped the wiggles... "oh yay"...
Why was it wiggling..?
I'm guessing, it might be a failing power supply.. in that, maybe the fan is sending 60-htz feedback through a defective filter cap or zener..?
Maybe it's a drying-out leaky filter electrolytic..?
If it were a wobbly hd motor-bearing, or wobbly-disk, I'm guessing the reset to 75-htz wouldn't have stopped the wiggles..?
Do defective hd's ever pump feedback to screen ccts..?
What do you think made those vertical screen-wiggles?..