I was about to post a very similar question, and it sounds very much
like the same problem:

An Asus A7V board in a generic full tower. Has worked fine for a
couple of years. Several months ago, whenever I would try to power up,
the machine would emit a sound similar to a european policecar siren.
Processor burned out, I blamed it on the fan.
Replaced the processor, got a stronger fan. Everything ran great
except when the soundcard was hooked up, the machine would suddenly
click off and reboot.
Put in a differenct soundcard, same problem. Switched soundcard to a
different PCI slot and everything works great, until I try to put the
cover on the machine. When I do, the machine suddenly clicks off after
a few minutes running like it did with the soundcard.
Tonight I got the police siren again.

So I'm thinking it has something to do with the case. Does this sound
like the same problem, and if so, how does one check to see if the
case is grounded, and correct it if it's not. I've never run into a
case issue before.

Many thanks for any advice.

> Tonight I got the police siren again.
>
> So I'm thinking it has something to do with the case. Does this sound
> like the same problem, and if so, how does one check to see if the
> case is grounded, and correct it if it's not. I've never run into a
> case issue before.
>
The case is grounded through the power cord. The siren is CPU overheating or
fan alarm. BIOS has options for CPU temperature and fan speed alarm.

ravic <(E-Mail Removed)> wrote in message news:<(E-Mail Removed)>...

> An Asus A7V board in a generic full tower. Has worked fine for a
> couple of years. Several months ago, whenever I would try to power up,
> the machine would emit a sound similar to a european policecar siren.
> Processor burned out, I blamed it on the fan.
> Replaced the processor, got a stronger fan. Everything ran great
> except when the soundcard was hooked up, the machine would suddenly
> click off and reboot.
> Put in a different soundcard, same problem. Switched soundcard to a
> different PCI slot and everything works great, until I try to put the
> cover on the machine. When I do, the machine suddenly clicks off after
> a few minutes running like it did with the soundcard.
> Tonight I got the police siren again.
>
> So I'm thinking it has something to do with the case

Your case is grounded unless it's made of plastic, you're using a
2-wire AC adapter plug, or your AC wall outlets don't have their
ground prongs connected to anything. And even though I'd never run a
system ungrounded, an ungrounded case shouldn't cause the problems
you're describing

I'd check very carefully for any shorts to the case, especially at the
mounting holes and the corners. Look carefully at both sides of each
hole, and unless you can prove that nothing around a side of a hole
can possibly cause a short, even if the motherboard is shifted around,
install a fiber or nylon washer there. The only times you don't need
such a washer are when the hole is surrounded by a copper donut or is
surrounded by no metal within 3/16" from the circumference of the
hole. It's perfectly acceptable to install an insulating washer on
top and bottom of each hole and rely upon the power supply connectors
for all the grounding. Also be sure that the motherboard can't touch
the case at the corners if either it or the case flexes. Support the
motherboard within 1-2" of each corner, either by installing support
posts in it (trim nylon ones for the right height) or by sticking
rubber bumper feet against the case.

I think your chip set may have suffered some damage from a short, but
try a new CMOS battery because low CMOS voltage sometimes causes the
police siren sound.