How can I reinstall Snow Leopard when my DVD drive is not working? How can I reinstall Snow Leopard when my external firewire DVD drive is not working?

A few weeks ago I got the typical signs of drive failure so I got Scannerz and tested it (http://www.scsc-online.com/Scannerz.html) and the drive was certainly full of bad sectors so I decided to replace the drive. Today I finally had time to go to a local electronics store and get a drive. I installed the drive, which was a piece of cake. 

Unfortunately, about a year ago my optical drive failed (do these things EVER last???) so instead of opening up the unit and replacing it I bought an external FireWire optical drive. It works great, it's a half-height drive and if it goes bad I can easily replace it. It's easy to work with. I've made music CDs, backups etc. etc. without any problems

Well, after putting the new HD in, I plugged in the FireWire optical drive, started the system while holding the alt key while booting, picked the optical drive with the original install media in it, and it starts booting. However, it never gets beyond the Apple with a white background with the spinner running underneath it. I hear noises coming from the optical drive that sound likes it reading, but it never gets beyond that.

I thought maybe the media was bad, so I put it in another Mac and it could be read. I thought maybe the optical drive had gone bad, so I tested that in another system and it too is working fine. I finally put the media in the FireWire drive in another system and it reads it (won't install it, but I didn't expect it to since it's not the orignal system). Therefore, there is no problem with the FireWire drive or the media.

Is there some trick I don't know about to get this thing to use the external FireWire optical drive for booting the install media? It's almost like it isn't being allowed to boot the system. I was thinking maybe I need to reset some parameters to make the FireWire a valid installation unit. Does anyone know anything about this?
I have no idea why the FireWire external drive didn't work, but the following did:


I took a neighbors Mac Mini and put it into target disk mode
I connected the Mini to my unit via FireWire
I put the media into the Mac Mini
I booted my unit holding the alt key down
When the list of available boot drives/media showed up, the OS install disk was showing up
I selected the optical drive (from the Mac Mini)
I installed the OS


I have no idea why this would work but my external FireWire optical drive wouldn't. It was incredibly slow but it did get the job done.

Although this is a solution, and maybe something that may be of use to someone else, I still have no idea why the external FireWire optical drive wouldn't work.