[newbie] eth0 at boot up

[NERILL]

i cannot get Linux to boot up with eth0 ( ethernet card) up and running. I am 
obliged to go to 'netcfg' and 'interfaces' and activate it manually. It says 
'eth0 failed' at one of the bootup script commands. I do save 'save 
configuration' to no avail. I have Mandrake v7.0. How can i do it 
automatically at startup?