HDD gone bad?
For file transfers between my house and van, I've been using a 20GB 2.5" hdd in a USB enclosure. This drive came out of my old laptop that fell off a shelf and shattered the screen.
After it fell, the laptop seemed to work alright with an external monitor. After a while though (few months?), it wouldn't boot up right. It would start up, but after a couple minutes shut itself off. Every subsequent boot within a few hours would result in a quicker and quicker shutoff. I thought it was something wrong with the MB, but after I tried the hdd in my vanputer and it did the same thing, did I realize it was the hdd (have no idea how or why).
So I got another hdd and the USB enclosure, and formatted the bad drive, and it seemed to work fine. But recently, it almost seems like the hdd is doing the same thing again. After connecting it, it works okay for a bit, then shuts itself down, in the middle of file transfers or defrag or whatever. Sometimes it comes back on, but then shuts down again, etc. I'm having trouble keeping it on long enough to transfer the files off and format it.
Basically this drawn-out story is asking: is this a dying hdd? Is it the hdd or the enclosure? What exactly happens to hdds when they start going bad? I got the original laptop in 2000.
There are different symptoms for different types of failures.
I personally had this happen to me when the motor unit on my drive was bad.