Hi
You need to enable route map.
interface FastEthernet 0
ip nat inside
interface atm 0
ip nat outside
backup delay 1 1
backup interface Dialer 1
interface BRI 0
no ip address
dialer rotary-group 1
interface Dialer 1
ip nat outside
access-list 1 permit
dialer-list 1 protocol ip permit
ip nat inside source route-map interface 0 overload
ip nat inside source route-map Dialer interface Dialer 1 overload
route-map permit 10
match ip address 1
match interface 0
route-map Dialer permit 10
match ip address 1
match interface Dialer 1
ip route 0.0.0.0 0.0.0.0 0
ip route 0.0.0.0 0.0.0.0 Dialer 1
Regards
JD