The graphics chip on the X505 series and a few others tend to overheat and this causes the solder joints on the motherboard to crack and fail. New motherboards are available on ebay. There are also repair services to reflow the solder joints. You might even be able to repair it yourself with a heatgun like people do with RRoD Xboxes but that's probably above your skill level.
I seen numerous laptop hard drives that failed because they got hot and oxidized the contacts between the controller pcb and the platter/head assy. I suspect at least some of the "freezer fixes" are just due to the contacts contracting and expanding onto non-oxidized surfaces. As for opening the platter/head assy, that's for when the drive is toast and you have nothing to lose. I've heard of people opening them and reassembling them inside a sealed bag or plexiglass box.