A couple of beeps, them dead

[cyril_madrid]

Something strange happens to my computer : after sometime of working I hear a beep, sometimes a serie of beeps, then the computer is turned off within 1-2 seconds. Sometimes when I reinitiate, almost immediately -when it goes through the BIOS-, I hear this same beep, and it turns down again.

I am using Windows XP Professional, I checked my memory with Memtest, fine.

I thought I might need to change the battery of the motherboard ? But haven't found anything in the forums saying that could be the reason.

Please help.
I am not an IT Pro, so please be explicit on your answer.