Mac peripherals forum: Impossible to start on Tiger or Leopard on My Firewire WD

Hello everybody

I bought a Western Digital My Book Studio 1Tb with Firewire and USB2.
I installed Tiger on it and I tried to boot on the Tiger partition on my Book Studio
I have an iMac PPC G5 with Leopard 10.5.8 and I can boot on my LaCie Firewire Disk which is 10.5.8 also.
The system profiler see both my WD Studio book and my LaCie on both firewire ports
Both Firewire ports and busses are OK.
The System preference see both firewire disk, Lacie and WD, on start up preferences.
I tried to startup on My WD studio Book by selecting it in start up preference. It won't work.
I got the interrogation point and then the start up is complete on my internat disk.
I tried to start up by pressing the ALT OPTION key on start up and I got the blue screen where I can see and select all my start up disc and HERE, I never saw the WD Studio Book. I can only see my LaCie Disk.
I erase all the WD Studio book and I installed Leopard on it. I disconnect the Lacie disk, I tried everything.
Each time, the WD Studio book is seen in the preference start up as a possible start up disc but it is never seen in the ALT OPTION screen on start up.

Does somebody have a great idea to solve this ? I would like to give my LaCie disk to my daughter and keep the WD as alternate start up disk, but it seems impossible and I am going to be disapointed not to have bought another Lacie....