Vista - Please advise where to seek help?

This is a HARDWARE problem
Have Acer Aspire M5100 deesktop pc, Windoes Vista Home premium, just over a
year old.
Was running normally, then total freeze - mouse/keyboard locked, only
option, power-off via mains switch.
Re-boot failed - didn't even get POST or BIOS screen. DVD drive spun (was a
non-system CD in it) but no hard disk activity - only sound was inside the
case, a tiny series of "clicks" like electrical low-voltage make/break,
though I couldn't see any sparks.

Re-seated all cable connectors. Pc eventually re-booted - normally, with
one exception - no sound. No Windows sounds, no streamed radio, no mp3
files play. (and I did check the "sound card" volume - is not zero). Then
froze again, so repeated the re-seating procedure.

Today - pc booted normally (except still no sound).

My first thought is that it's possibly a faulty PSU (it's only 250w), but
given the sound failure could it possibly be a failing m/bd? (it's an
integrated sound chip)

My problem is the instability of the pc, NOT the sound fault (which is the
only symptom I can detect when it's working).

Has anyone had experience of this?

PC is "as is" when bought - only time the case was opened was when it
failed, yesterday, so there's no internal modification. Peripherals are
connected via a powered 7 port hub, so no excessive load on the PSU.

FWIW - tried ACER's forum, which offers an e_mail, BUT it's not possible to
get an e_mail to them. Starting the questionnaire results in immediate
re-direction to FAQ's, drivers, etc - no e_mail.