computer will not boot!

my daughter told me her computer would not start, so I tried to reboot it numerous times but it will not go past screen that says at bottom 'press delete to enter setup' and 'press tab to see bios post message. pressing delete or tab gets no response, only once did it go to bios but once there it froze and I had to reboot and I haven't been able to get to bios again. I loaded the xp o/s disc but it won't boot from disc. opened computer to check for any loose wires but couldn't see anything obvious. daughter told me when it was going ,if she left it for a while it would turn itself off, don't know if that is related. as I have said it uses xp ,I think it uses an intel Celeron processor, 2 gb I think, has 4gb ram , asus motherboard, western digital 160gb harddrive, my computer knowledge is limlted so be gentle

 

if the computer is left switched on and it turns itself off after a while sounds like a overheating issue. Check all the fans to see if they are spinning correctly especially the cpu fan.

 

it has 2 fans both are working fine

 

Also I would check to see if the memory is sitting in properly in the motherboard as this sometimes stops the computer from booting.

 

checked memory, seemed ok ,but pulled it out and back in, booted computer and got to screen to enter f1 to continue or delete to enter setup, I chose f1 and got to desktop, I reinstalled windows, ran malwarebytes to check for malware and did disc clean and defrag, it seems to be working for now, my daughter tells me it used to as well as turning off randomly would also turn on for no apparent reason, I can confirm that, because before her computer was moved to her room, it was out next to my computer and I was home alone one day when it just turned itself on, scared the bejeebees out of me, anyway now that its going is there anything I should check so that we don't have this problem again. thanks for your input

 

This could be a long shot but in my thinking process that pulling memory out and back in again it could be that a bad combination of sticks. you need to get the same sticks of memory.

 

check for poltergeist... or malware (as in the malware thread)

 

A computer that turns itself on has some setting, perhaps in the BIOS, that sets it to do this.
I inherited a 1/2 dead computer that did this. Until I could figure out why it turned itself on each evening, I connected it to a power strip and shut off the power to the computer.

The computer had been used in an office and was set to turn on and update things at night when the office was closed.

I had a wake on LAN setting I needed to disable.
Have a look in the BIOS for Wake on schedule or Wake on LAN or scheduled start, disable it and the computer will not power up by itself.

 

Over time the RAM modules can unseat themselves to the point where a poor connection is created at the pins. Re-seating them like you did often solves a host of weird issues. You can also get a copy of the Ultimate Boot CD, burn it to a bootable disc with a free program like ImgBurn, and it has various diagnostic tools for hardware including MemTest which performs a RAM diagnostic.

As plodr suggested, check for the "Wake on LAN" settings, and make sure "Boot via PXE" is disabled in the BIOS.