upgrading from tiger to snow leopard without an optical drive

I am currently running 10.4- Tiger. I never updated because my optical drive went out and I never got it fixed. I called Apple and they said that I could upgrade to Snow Leopard, but not Lion. So I have purchased Snow Leopard, but don't know how to load it. Here's what I've tried:
1) Remote Install- from an imac and mac mini. It won't recognize the connection.
2) I made an .iso of my Snow Leopard disc in disc utility. I put it on a flash drive and tried to boot. No going. I also tried to mount the .cdr directly from my desktop. It goes through the beginning prompts and then says that I need to reboot to begin installation. I suppose when it reboots, it loses the mount and doesn't begin the installation.
Long story short, any suggestions?

Did you turn on System Preferences > Sharing > DVD or CD Sharing?

Kaveman- yes, on both computers. I previously talked with Apple support and the tech didn't think that it would work because it wasn't a Mac Air (not sure why that would matter though).

I'd start this by giving the Tiger Harddrive a nice descriptive name.
Then plug it into the iMac with a FireWire Cable.
Restart the Tiger while holding down the T key, this will start it up in target mode, a large FireWire symbols will move around the screen.
Now, put the Installer DVD into the iMac and run the Installer.
When it asked what drive, choose the Tiger drive.
Proceed as normal.
Once you've finished, Restart the no longer Tiger and it should boot into SL.