BDC in 2k3 server

Hi,
Guys I am having two HP servers both are running 2k3 server one is using ads.dhcp.i want to make another server as my backup server if my PDC
fails i want to up another server.

for this i must create backup server can any one help me how to create backup domain controller in 2003 server.and how to make BDC as PDC
if my PDC goes down

Thanks in Advance
jnr