Hi!
My DVD drive is dead and I need to reinstall Tiger.
Is it possible to do it by writing the DVD iso image to a
second HDD and booting the instalation from it?
How can I write the iso image to that HDD?
Thanks!

Looks like you have yourself in a bit of a pickle. I can't say that I envy you, so I'll just take this opportunity to laugh: Ha Ha Ha!

Okay, seriously, I really doubt that you'd be able to do that. My advice would be to pull your hard drive out of your Mac, attach it to another Mac, and install your OS from another machine. Once you've finished the install, just slip your hard drive back into your G4, and all will be right with the world.

I admit, this procedure sounds a lot like sodomy, but the alternative is to get your Mac repaired so that you can do the installation the proper way. :P

Gay men don't jump.

That will work but there might be an easier way assuming
this advice isn't too late. If you have a second computer
with a DVD drive and both computers have firewire ports
this solution will be easy. You will also need a 6-pin to 6-
pin firewire cable. Start the computer you want to install
Tiger on while holding the 'T' key down. You should soon
see a large firewire symbol bouncing around on the
screen. On the second computer place the OS X 10.4
install disk in the optical drive and click on the disk then
choose "Install OS X". Your computer will restart from the
CD to install the OS. While this is happening connect the
firewire cable between the two machines. On the second
computer progress through the screens until you come to
the option where you select the destination volume. You
should see two drives, one being the interal drive from the
machine you are using and the other should be the first
computer with the firewire symbol on it. Select the first
computer's hard drive and proceed from there. Simple!

Good luck!