[Long post] Continuous Siren from motherboard when booting happen intermittently (P4 3.0 old socket)

Please advise!!!

I am having problem with a custom motherboard with unknown
manufacturer, The only thing I know about it is the PC brand which is
PURO. The motherboard PCB also have PURO etched in the serial number. I
will post the serial number again later.

The motherboard processor use to be P4 3.2 Ghz. Now the suplier change
it to 3.0 GHz processor, most probably thinking that the downgrade will
solve the problem. But it doesn't. If you have ever heard of FTEC, stay
away from it. I forgot what is the socket name. But it is the old one
because I can't buy new motherboard to change/upgrade.

The symptom is like this. During boot, not even displaying any text,
the screen just blank, it will keep wailing the siren continously.
Sometime this happen sometime the pc boot and then I can use the PC.
Sometime when using the PC, it will automatically restart and give the
wailing siren with blank screen.

In the beginning I thought the problem is CPU overheating. I know that
P4 is famous for its heat problem. I thought it is that problem because
during boot two thing will happen.

1. The fan sound go very noisy for about 10 second and the wailing
siren will happen after that.
OR
2. The fan sound go very noisy for about 3 second and then it will go
quiet (but still spinning). That is the sign of successfull boot. The
computer will boot to XP and be useable.

However I have double check the CPU thermal compound and add aditional
fan to improve air circulation. After service by the suplier (FTEC
again!!!) I notice two thing and rectivy both of em. (1) The technician
apply too much thermal compound, very sloppy. (2) Both fan for the very
small case are intake fan. So I remove excess thermal compound and add
another fan to blow hot air out of the case. To make it shot, if it
ever have heating problem, I am confident that it has been fixed.

The other reason that make me thing it is not a heat problem is that
this usually happen during first boot in the day. And the fact that
this happen intermittently (50% of the time).

Bellow is my MBM 5 log that show temperature and voltage. I might have
configured the temperature sensor wrongly. I will double check that
later. Now I'm a little bit paranoid to restart this PC because I don't
want to hear the sound of unlucky reboot.

The interval is 30 second, so bellow is about 5 minutes of log right
after booting into XP.

| Case | CPU | Core 0 | CPU/IO
---------------------------------------------------------------
| 35° C | 26° C | 1,26 V | 1,46 V
| 36° C | 26° C | 1,25 V | 1,52 V
| 35° C | 28° C | 1,25 V | 1,49 V
| 36° C | 25° C | 1,26 V | 1,47 V
| 37° C | 27° C | 1,23 V | 1,50 V
| 36° C | 24° C | 1,25 V | 1,49 V
| 35° C | 27° C | 1,23 V | 1,50 V
| 36° C | 24° C | 1,22 V | 1,47 V
| 37° C | 26° C | 1,25 V | 1,49 V
| 35° C | 26° C | 1,25 V | 1,49 V


| +3.3 | +5.00 | +12.00 | -12.00 | -5.00
----------------------------------------------------------------------------

| 3,31 V | 5,08 V | 11,80 V | -13,26 V | 3,45 V
| 3,34 V | 5,11 V | 11,92 V | -12,68 V | 3,60 V
| 3,33 V | 5,11 V | 11,92 V | -12,68 V | 3,50 V
| 3,36 V | 5,11 V | 11,92 V | -12,68 V | 3,50 V
| 3,31 V | 5,00 V | 11,86 V | -12,77 V | 3,45 V
| 3,38 V | 5,08 V | 11,86 V | -12,85 V | 3,40 V
| 3,36 V | 5,13 V | 11,86 V | -12,68 V | 3,65 V
| 3,39 V | 5,11 V | 11,92 V | -12,27 V | 3,60 V
| 3,34 V | 5,00 V | 11,73 V | -12,52 V | 3,50 V
| 3,34 V | 5,13 V | 11,92 V | -12,68 V | 3,40 V


| Fan 1 | Fan 2 |
---------------------------------
| 675000 RPM | 75000 RPM
| 42187 RPM | 0 RPM
| 84375 RPM | 168750 RPM
| 112500 RPM | 675000 RPM
| 0 RPM | 675000 RPM
| 337500 RPM | 84375 RPM
| 0 RPM | 675000 RPM
| 0 RPM | 84375 RPM
| 0 RPM | 0 RPM
| 0 RPM | 675000 RPM

The fan data is erratic but I know they are working.

-5V is 3.5V !!! Is this normal?

Case and CPU temperature looks like switched.

Thanks in advance. I really-really need help!!!