How do I upgrade my iMac g3 from 9.0 to 10.4?

Dead cosmiconion,

No need to post again. Your question is being answered in the thread you started in the Intel iMac forum here:

Vintage iMac g3 DV400 upgrade

Yes, the other thread is technically in the forum for newer iMacs but it is being served there. If you wish us to have the Hosts move the other thread to this forum (the proper one for pre-2006 iMacs) we can easily do that and have the duplicate removed.

Wow! You're experiencing seller's remorse. I have a green iMacDV 400 that I bought at least 6 or 7 years ago at a thrift store. I upgraded the memory to 1 GB, the HDD to 80 GBs (128 GBs is the maximum for native recognition), and the OS to 10.3.9 and 9.2.2. As they age, the slot-loading models tend to develop failure of the P-A-V (Power-Analog-Video) board, because their convection cooling wasn't adequate. This isn't an easy repair and involves risk of electric shock, unless you're skilled at discharging the high voltage that's stored for months and sometimes longer. For this reason alone, I wouldn't recommend that someone buy a used one now or start upgrading one unless all hardware purchases can be found at very little cost. Since you're willing to take the plunge, start with the hard drive and buy at least one 512 MB SDRAM PC-100/133 CL-2 card. You can always buy a second memory card (check the prices here) later, if you think you'd like to max it out. Check ebay for a retail (black with large "X") installer DVD of Panther or Tiger. Have you checked to be sure that the original DVD-ROM drive hasn't been replaced with a CD-ROM or CD-RW drive from another iMac? Does it still read DVDs? There's also an age-related problem with those slot-loading optical drives, in which the internal rubber rollers lose their natural pliability/grip, required for grabbing the disks on insertion and proper ejection. Some disks barely make it in or out, past the front plastic housing. If you wanted to go overboard, you could buy this expensive internal DVD±RW drive for the slot-loading iMacs. As I mentioned, a failed PAV board usually means retiring the computer. There are no new replacement parts and buying a used one with questionable remaining service life is typically an exercise in futility. For all of the potential headaches you could experience, it's difficult to advise anyone to invest a lot of money in a 17-18 year-old iMac.