hi what could be the problem with my computer. whenever i turn it on, i can hear it start, the funs run but only for a short while the3n it goes off. switch it off from the mains and on again the4 process is repeated. help

Try resetting your pc's BIOS, if you have your motherboard manual it may tell you how to do this. It is usually a matter of moving a little blue "jumper" over two contact pins. Alternatively you could try taking out the motherboard battery, leaving it for a minute or two, then replacing it and trying again.