Thanx eddie11c,
I will try your new solution later,but tell me if I get endless reboot loop again,how can I uninstall EFI ?And I must tell you that the disk ID of Leopard is different in Tiger (Last time as I remember it is disk0s1,and It keeps changing,dose that makes mistake?)And what is the slight difference between command "hdiutl unmount" and "diskutil umnount"?--I have checked the man of "hdiutl" and got no clues --:-)

Since I can NOT boot from DVD I suddenly come across an idear of installing Leopard from Tiger use ISO by Pacifist,but there are so many folders in ISO and I am confused which one to choose and the install order cos there are many packages with the same names.Could you please write a HOW-TO with detailed instructions to install by HDD for me?

Thanx a million!!

Regards!

Kael