I've a laptop here that when turned on powers off after about 9 secs (before video is initialized). I was thinking it was overheating BUT this is what's really odd: if I hold down a key on the keyboard it will stay on and even boot the OS. Until I release the key, then it shuts off in 9 secs.
This would seem to rule out overheating and the PSU. Any ideas what it might be?