Dell Dimension PC powering off

Hi

I have a Dell Dimension PC running Windows XP which was working fine until a couple of days ago. However now when I power it up, it runs for about 5 seconds and then powers straight off again. It appears to be starting up normally i.e. Dell logo and startup appears etc. however it just powers off again after about 5 seconds.

I have replaced the power cable with a new one but the problem is still occuring. I spoke to a Computer technician who said an electrical component on the motherboard has probably failed and that it would not be viable to repair the machine given its age (8 years).

Before I consign it to the server room in the sky just want to check if there is anything else I can do with it.

Thanks
Corbomite1