(probably OT) Acer Aspire 7535G mostly dead

For another friend, this (Vista era, but more than adequate for her
needs) 17" laptop. Virtually new condition, as she took care of it.

When power supply connected, blue line through power button, and light
on front, lights.

When power button pressed, ring comes on (lights up) around power
button, and another light on front lights. This and all subsequent
description applies whether on external or battery power; the only
difference external power makes is the light line in the power switch
and the light at the front. (System seems to have charged the battery.)

Nothing happens on screen - no even sign of backlight coming on.
(Thought - _could_ be screen/backlight, but we don't get Windows sounds
after the usual delay either, so I think it's mobo/processor. Have tried
with external monitor [no display], but not sure at what point
Fn-key-plus-F-key-to-change-monitors works.)

Fan runs; DVD drive makes its usual twitch.

The two things that make me think it's not completely dead:
o pressing a button on the left that has a picture on it that could be
an SD card makes that button flash for a second or two.
o turning the machine off (i. e. back to dead [DVD won't eject, no
lights other than external power if connected, fan stops]) by holding
the power button in works, _but requires it to be held in for several
seconds_.

Behaviour is the same with: only either one of the two RAM modules
present; HDD removed. I've dismantled the unit as far as I am willing
to, and no sign of loose or damaged connectors or any distress (charring
etc.); just reconnecting power-button board and keyboard while in that
state, and after reassembling whole machine - no difference.

Not important - we've written it off, and ordered a replacement (a
Compaq; nobody had a 7535G for sale, other than a broken one or a
motherboard, both of which we decided were too much bother to try, given
the asking price), but if anyone _does_ know anything about this, it'd
be intellectually satisfying to fix it. (I did Google; the most
promising was suggested by more than one, and one called it something
like an "ATX reset", being to hold the power button in for 30-45
seconds; I did that with and without battery/ext. power connected, with
no change.)

It had been running W7 fine - home premium, upgraded from Vista before
my eyes using proper upgrade discs (which I still have) when I bought it
about 5 years ago we think - but that's _probably_ irrelevant (so OT for
here) as it behaves identically with the hard disc absent.
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

"A great many people think they are thinking when they are merely rearranging
their prejudices." - William James