Okay, my 2 cents. First, the majority of my computers have been laptops. And maybe I've just had good luck, but I haven't had that many (what was it? 30%?) fail on me. Obviously, batteries don't last, but I've only had one die from something else. I still have my first one, a IBM 486, and someone gave me a 386. Both still boot up when plugged in.
Being a scavenger and a packrat, I "obtain" a fair amount of dead computers. This one that I am using mostly I found at the curb, missing a hard drive, everything unplugged from the motherboard, and a bad power supply. I had both of these items, and when it booted, I found a P4, 3 GHZ w/ hyperthreading(the predecessor to dual core processors). I added a DVD burner w/ LightScribe (open box sale at the discount local computer store-$19.00), and $6.00 for cables to attach a second HD(also already had).
I can't say enough about these HD enclosures. Best money I ever spent. I have 5 of them, 2 for 2.5 laptop size HDs, and 2 for 3.5 HDs, and 1 that does 3.5 and CD IDE drives. In addition to those, I also have a cable that does all IDE and Sata HDs. When you have a PILE of HDs, these are the best way to back up.