Just today, I managed to get a broken IDE drive spinning again by replacing its PCB with an identical one. Unfortunately, I suspect that there are problems with the IDE -> USB enclosure that it is connected to. When I connect the drive via the enclosure's USB cable to my desktop PC and power it on, it keeps reconnecting every second. The disk shows up briefly in "My Computer" (albeit non-clickable and without any information) and then disappears again. Every time it connects, a prompt appears, asking me to format the drive.
I also connected the drive to a laptop. Strangely, this time the drive was't detected at all.
The drive did manage connect properly once: After a dozen of prompts and reconnects, Windows suddenly "held on" to the drive and started reading its contents, allowing to explore the drive. Unfortunately, this hasn't happened again since.