HELP!unable to start windows

i use winXP,when i start my pc and it displays:

Windows cannot start because the following file is missing or corrupt

WINDOWS/SYSTEM32/CONFIG/SYSTEM

you can try to fix this prob by insert original setup cd and press ‘r’ at the firdt screen to repair it.

i’ve inserted the cd and press r at the first page but it still the same…what shall i do???