Regarding external drives, I had a problem with an external 500GB Lacie drive. It started having trouble initialising on startup. You could hear it spin up, but then it sounded like it was having trouble reading and kept trying for ages until eventually it succeeded and then appear to the system. Sometimes this could take 10 minutes. I did some searching and found some other people having this issue, and it turned out to be the enclosure's PSU and not the drive itself. I removed the drive from the case, which turned out to be an SATA Seagate 7200.10 and identical model to my other internal ones, installed it inside my main PC, and it has worked perfectly ever since.

I was trying to think about internal drives I've owned that have failed and can't think of much. The only complete failure was a very old 1.2GB drive in my A1200 many years ago. Forget the make, but it might have been Conner.

I've had a few laptop HDDs fail on family or friends laptops, but that is to be expected I suppose. At least newer 2.5" drives are now seeing better shock detection systems to prevent this.

The only other one I can think if was an IDE 160GB Maxtor drive being used as an XP boot drive, which started to generate bad sector errors during booting. I swapped it over for a larger SATA drive and used Maxtor/Seagate tools on it and managed to fix it. I think it just had a couple of bad sectors that the software designated off limits after a full scan, and a partition and format later the drive was working perfectly again. In fact it is still working in my download PC.