Fedora 15 uses a new system / service called systemd. ntsysv is not available to enable or disable services. You could also use:
# system-config-services <enter>
system-config-services shows you a GUI from where you can select the services to enable or disable.
Alternatively, if you are comfortable with the command line, perform following to disable startup services in fedora 15
# cd /lib/services/system <enter>
# systemctl -disable servicefile*.service <enter>
where servicefile is the name of the service you want to disable.
# chkconfig servicename off <enter>
which is the right approach and where servicename is the name of the service you want to switch off.
I turned off iscsi, iscsid, livesys, livesys-late, sendmail, netfs, abrt-oops, abrt-ccpps, abrtd