When I Turn on thePower, my Conmputer just turned off by it self and start again and switch off again and so on.

Apply new turmal compound to your cpu and try to start again

wrong that mobo is not blue and is not made by intel.com at all
it is ASUS..com
says so on the mobo
and at their web sets all mobo sold by them from 1995 to
2022, have QVL LIST ON CPU, ALL DO THERE.
SO FIND IT OR ASK THEM.
TOOK ME 3 SECONDS TO FIND THIS GOOGLE


https://www.asus.com/us/SupportOnly/P5S-MX%20SE/HelpDesk_CPU/

QVL = QUALIFIED VENDOR LISTS, RAM OR CPU
FROM 1995 TO NOW, AND ASUS.IS THE BEST DYI MOBO MAKER BAR NONE, AND GIGABYTES TOO. 2ND FIDDLE.

Try this Make sure no game in ps3 turn ps3 off and by the switch at the back unplug it wait a couple of sec then plug it back in turn on buy the switch at the back then hold down power and eject hear a beep keep both preseec till 2nd beep let go should be able set it to ya tv

a real answer. not bs above.
you proved the PSU is ok, why go there?
the why this works is the chip called South bridge.
does all this (this is how (also) the windows start button and shut off works, called SOFT POWER OFF)
the button on the front panel is a N.O SPST switch.
normally open momentary and shorts a specific and non world standard pin on that mobo to ground, (adjacent pin)
this sends a logic zero state (0v) to the South bridge
then it turns on a transistor on that mobo and that grounds pin 16 to PSU, and PSU magcially turns on.,
end theory101....
the problem can be ; the switch is plugged in wrong. or bad.
HP uses vast numbers of MOBO in PCs so have all different pinouts. and hard super hard to trace and learn that.!
all mine are keyed, and the mobo is silk-screened painted, Front panel.
the other possible is that the PSU is not putting out standby power
on pin 9, with PSU plugged into the wall pin 9 must be at 5vdc.
if not the South Bridge will be dead.
as will the power switch it supports

http://www.pcdied.com/power.html

The South bridge runs power. managment.
the 945P must have PSU standby power and the switch most reach its power on pin, or there will be no working switch ever.

The PC can also force the PSU off if one of the onboard
power regulators are reading wrong (say too high)
The power management is complex, but not that one pin,.below.

Power management,
wake on LAN, sleep, hibernate. and more.
but all we care is the power switch but if the above features work then the switch is bad, and why I mention that.

my PC can even self turn on at 6am if I want, (a bios features) self power on...


now the list of simple..tests,etc.
1: PSU pin 9 must be 5vdc at all times, wall plug aC connected.
and if read of PSU has a switch, set to logic 1 , (1/0 labled)
means on.
2: the correct working switch in front panel,
2b< that switch must be on the correct jack on the mobo and not off one pin or some other ERROR. there.
3:the PSU good ... some are not, (complex reasons) skip i will.
4: the MOBO most be good, (and not overheated)
Switch.
will the PSU turn on if dvd/cd drive and HDD drive cables pulled.?
even pull RAM. sticks? it will beep like mad but will turn on.
and be dead but turns on. like that. well most do.
5: jump the pin below, does that turn on the PC? as it must!

A DT PC 12 years old now.


m7480n this PC is now retired at HP means zero support.
no service book but it lacked the power jack info in most cases

DATA: (first know what is there, the mobo is clearly labeled. look?
this is the best search I did for you,at HP real, yours

• Manufacturer: Asus
• Motherboard Name: P5LP-LE
• HP/Compaq motherboard name: Emery-UL8E

ive owned many P5 in my life, not now but am an ASUS guy.

but this old board we can do research on it,
I like HP and HP likes ASUS as do I. both.
knowing this fact
we see
Asus Leonite P5LP-LE User Manual

then we find the book on it next like this, (took me 1second )
page 5 shows layout


https://www.manualslib.com/download/449087/Asus-Leonite-P5lp-Le.html


bottom right shows, (F_panel) Bingo, on jack.

page 25 covers that jack
so pull the jack there pull plug from jack
then jump pin gnd /pwr pins with screw driver tip.
if PC turns on the switch was bad or plugged in wrong,
if not the PSU is dead, Standby power is dead, pin 9

Asus books always show all this, but never HP for some odd reason. (details like this)
good luck

You should unplug the power cord from the power supply, pop out the cmos battery, switch the bios reset jumper to the 2 and 3 pins, wait about a minute, put the jumper back to 1 and 2 pins, put cmos battery back in, plug in power cord to psu and turn on pc. If you have any issues with this process please refer to your owner manual for the motherboard or look one up on their website. Please let me know if this fixes your issue.

Try taken the bios battery out for about 30 secs, replace it and then reboot, after post press F8 untill you have a screen pop up with a safe mode option use the arrows keys to navigate to safe mode and press enter. In safe mode goto my conputer c:drive(boot drive) windows. In the windows folder look for a file called prefetch, delete all it contents. Exit out of everything and restart the pc. If same thing happens post back.

The drive is bad, I had a similar problem with a WD HDD, You can download Seatools and work on it in DOS, http://www.seagate.com/www/en-us/support/downloads/seatools

Did you install the drivers for the motherboard already? If so check the connections from the power switch to the board which all should be on the bottom right of your mobo. I switched a + and - one time and it went into a infinite look of turning on and off = / Beyond that ASUS Customer support sucks and I would just try to RMA it and start over.

This sounds like an overheat problem, is your cooling fan working properly, also the processor you are using is a powerful one, so needs a cooling fan much more powerful than the lesser powered athlon 64 processors.

Did you try to unplug all AC Power; remove internal surface battery; and then jumper the 'reset' pins from 1-2 to 2-3 ? Leave in this state for about 5 minutes- then replace battery; re-jumper back to pins 1-2- replace AC power cord. Sometimes wiping out the BIOS setup information and restarting/re-setting it up will do the trick!