Help ClockworkMod installed "for once time"

[Red Planet]

I have downloaded and installed from market ROM Manager, made update.zip. I have rebooted in native recovery, have executed install:update.zip. It has been installed ClockworkMod Recovery, now it is possible to install zips from a flash card, stable CyanogenMod has installed successfully. However after reboot in recovery mode it is started native recovery, instead of ClockworkMod. It is necessary to install each time Clockwork to install any zip (for example, update-cm-7.1.0-Legend-signed.zip). Why is ClockworkMod installed "for once time"?

 

[Red Planet]

I underdtood my mistake. ClockworkMod is executed, but not installed bacause my HTC Legend has S-ON protection. And I have to "install" (not install, but execute) ClockworkMod each time when I want to flash some zip.