NEED HELP (restart itself)

HP desktop
P4 XP SP2
so im getting confuse with this problem
when i came in the office, my pc its running, im sure that i shutdown it properly last night
it will not take long, and it will restart itself (properly shutdown, then start)
but later, when the restarting runs, it will not load the welcome screen it will restart again
i bring already in the shop to check the FANS and PSU, they say nothing problem
i got to scanned only the following:

AD-aware (no spyware)
Spybot S&D (it foud some but immunized them)
Zone Alarm AV & AS (nothing)
AVG (no luck, it will shutdown the pc before it finish the scan)
others Antispyware cant run because it shutdown then restart itself

im in hurry while logging this problem because maybe it will shutdown again and i cant post it
Luckily i got the HJT log and its attached
can somebody help me please

 

You are running 2 Antivirus applications, AVG7 and iSafe from Zone Alarm. Only install 1 Antivirus application on a computer, they will conflict with each other. Pick you uninstall the other.

The version of Java that is installed on your computer is out-of-date. Install version 1.5.0_07 available from http://www.java.com/en/download/manual.jsp. Make sure you uninstall all older versions of Java.

Scan with HijackThis and fix teh following lines:

Other than the above there are no visible infections in your HijackThis log.

 

thanks Shadow_Puter_Dude, im in the internet cafe as of now, because i think my problem in hardware
we try to take out one by one (except PSU) still same problem
all is checked
PSU
HDD
floppy drive
Cd drive

only the proccessor and mother board is not yet check because we dont have extra (in the shop) same item

but thanks a lot
i will try to post in HARDWARe section, maybe they can advice me something

thanks again