You may enable/disable services upon bootup by using the chkconfig command. You need to login as root (either su or su -) then run this command:
chkconfig --level <runlevel> <service> on/off
e.g. To disable samba on runlevel 3, 4 and 5 upon bootup, run this command:
chkconfig --level 345 smb off
To enable it again, run this command:
chkconfig --level 345 smb on
For more information about chkconfig, run:
man chkconfig