how can i add to "run once" a file to excute?

hei ,

i am making an unatendded Xp disc.

i need excute an cmd file acfter that to reboot

and the to excute another cmd file.

i added to my first cms an reg files thats adds to the "run once"

the second file.

but in registry i can write %systemdrive% ...

and the problem is that i cant give apath cause every one has

a different system drive.

how can i fix it?

to add the registry "run once" a variable like "%systemdrive%"