It's possible for an unstable +5V supply to impact on a HDD's performance and reliability, but I suspect that the most likely reason for the increased incidence of failure is that newer HDDs are less reliable than the older ones. They spin faster, have much higher data densities, and the heads fly much closer to the platters. Laptops are also affected by heat and vibration. In any case the +5VDC supply is derived from the adapter's 19VDC output via a DC-DC converter on the laptop's motherboard, so any instability in the adapter's output would be largely mitigated by the down-converter on the motherboard.
As for why "the AC power adapter wattage and type cannot be determined", the original Dell adapter has a third wire which connects to a Dallas / Maxim DS2501 IC inside the adapter. This IC contains a 512-byte memory which identifies the specifications of the adapter to the laptop's BIOS. It is possible that there is an intermittent break in the adapter's power cord.
http://www.laptop-junction.com/toast/co ... y-revealed
DS2502, Dallas Semiconductor / Maxim, 1Kbit Add-Only Memory, 1-wire:
http://datasheets.maximintegrated.com/en/ds/DS2502.pdf
http://www.chzsoft.de/storage/2501unw.pdf
(DS2501)
BTW, your tomshardware URL is broken.
Statistics: Posted by fzabkar — Today, 16:55