Yes it's possible with an iPod.
Hi,
To install 10.4 on an iMac G3 without a DVD drive you will need the following;
1. A Mac formatted iPod (min 3Gig free space) with Firewire cable. (I used an old iPod mini 4Gig).
2. iMac G3 with Firewire socket ad OS 10.3 installed (last to be shipped on CD).
3. A second Mac with 10.3 installed, a firewire connection and a DVD drive.
4. OS 10.4 install DVD.
This is useful if you have an old G3 at home, but use a more advanced computer at work.
Step 1.
Insert the 10.4 DVD in the second Mac and connect your iPod via Firewire. Let the computer mount both.
Step 2.
Now go to "Disk Utility" in the Utilities folder (MacIntosh HD/Applications/Utilities). Click on MacIntosh HD once on the left hand side, options such as First Aid, Erase, Restore etc. will appear on the right. Select "Restore".
Step 3.
Drag the DVD information (Mac OS X Install DVD) to the box marked "Source", and your iPod information to "Destination".
Click "Restore".
This can take 15 minutes or more.
[if this fails at this point, check your iPod is Mac formatted, it won't work on PC formatted iPods].
Step 4.
Now, take your iPod to the iMac G3 and connect via Firewire. Let it mount. Close all other applications.
Step 5.
Go to "System Preferences" and choose "Startup Disk" in the System section. Choose "Mac OS X.... on iPod". It should be obvious which one it is. Click "Restart".
Step 6.
The G3 will take a bit of time to start up, but you will be welcomed with the language selection screen after a minute or two, installation can then proceed as normal.
And that's it.
Regards,
Jamie