Also, remember that if it originally had a 4GB or 6GB Hard Drive in it (233, 266, and 333MHz iMacs) then you will only be able to get a 7 GB Hard Drive if you want 1 partition. The very early iMacs will only recognize the first 7GB's of the hard drive (maybe 6) if its larger than the original. So if you want to buy a 20GB hard drive you'll have to make the bootable partition no larger than 7GB (maybe even 6GB), and then use the rest for whatever you want to use it for.
CPU upgrades aren't worth it for that particular Mac. Yes, they're out there (PowerLogix made one for the early iMacs), but like everyone else said, they're gonna be too expensive. You'll end up paying more for the CPU upgrade than the whole computer is worth.
If you upgrade the RAM to at least 256MB it will run Panther really well. My mom has the original (Rev A) iMac, running at 233 MHz, with 256MB RAM, and a 6GB HD Upgrade and its runs Mac OS X.3.5 (Panther) beautifully!
If it only has 2MB of video ram in it, then you are able to buy another 2 or 4MB of RAM for it. I think its called SGRAM, and you'll have to look around to find it. This will allow you to run Mac OS X at 1024x768 with Millions of colors. Otherwise it will only run 1024x768 at Thousands of colors, or you can run 800x600 at Millions of colors.
If you need help changing the hard drive in it I can help you. Email me at
imac576@hotmail.com and I can give you step by step instructions. I've done this MANY times. Contrary to what an Apple Manual may say, you DO NOT have to take the logicboard off to get to the hard drive. The hard drive is under the CDROM Drive, so all you have to do is take the CDROM drive off which is very easy.
