Here's the deal:

H/W: MacMini - the original one 1.25 GHz PPC G4, 256 MB RAM (I know I will put 1GB stick ASAP) etc.

S/W: MacOS X 10.3.9

Wanted to install Leopard from original DVD media but this is what happens:
Method 1:
1. Boot with Leopard DVD in drive while holding C key - it finds the disk; it boots from it but then it just keeps on reading disk forever - okay I've waited for almost 2 hours; it still was showing dark screen with wait cursor spinning.

Method 2:
1. I've booted into 10.3; then mounted the install media; clicked on the Install link; clicked on the re-boot link; system boots back into 10.3.

I know that the OS disk is fine cause it came with MacBook Pro and I've verified that booting MacBook Pro with it gives me installation screen in less than a minute (booting with C key option). I've heard that media should support old PPC Macs as long as they are > 800 MHz CPU frequency, or I should at least get a message.


Is it not enough RAM, or am I doing something wrong?

Doing something wrong, the disks you get with Apple's machines are locked to that particular model you need a store bought Leopard install disk to upgrade your mini.

The disk I am using is actually a retail copy of Leopard; it's not the one included with Mac itself.

Well you say it came with the MacBook Pro in the first post so which is it? I know my retail Leopard copy installed fine on my G4 FW800 dual 1.42mhz with 1GB ram in it perhaps it is the 256mb stopping you then if it is a retail copy you bought at the store..

Bad wording on my end - I have a boxed/retail version of Leopard; anyhoo, I've just popped 1GB of RAM in the Mini. Keeping my fingers crossed. The machine booted like a charm and a whole gig is visible to the operating system; the system is stable. I will start installing... yet again...

I'm happy
256 MB of RAM has been the issue. Once I've popped in a 1GB stick the installation kicked in...

Update:
Installation complete - works like a charm. All updates installed.

Wait a minute... you're installing Leopard on the Mac Mini G4 with only 256mb of RAM?!

Yeah, that was just a failed attempt, until the next day when I got a 1GB stick of RAM. It works now This machine will be used to test web applications - so all it needs is Mac OS X 10.5.x with Safari, Firefox, Opera + maybe Microsoft Office 2008. I am not expecting much from it anyway.

Ahh. Good.
Make sure you have more than 512mb of RAM for leopard. My PowerMac G4 digital audio is 466Mhz has 2gb of RAM. And a Radeon 9800. Runs okay. But I'm pretty sure I need a faster CPU.

Hello there, I had exacatlly the same problem, with the first generation Macmini with 256MB RAM and 40 GB HD, that was yesterday, but today I tried it again with 512 MB, no donut for me!!

I was tring it with a Install DVD that came with a Mac Pro (the octa core) from the lab I do research.

It says in the instructions.localized folder in the DVD that it needs PPC or Intel with at least 512 MB RAM and 800Mhz, I'm with 1.25Ghz... Should it be due to the DVD that is blocked for other models or do I need more RAM??

When I attempted to install it gone for houers in the start up screen, but sometimes it appears a Classic os folder with an "?" inside, that blincks with the Mac OS Icon (the blue face)!!!!
Has anyone seen it, does anyone know what could it be??

Well, I also think it could be a problem with my optical drive, since it doesn't burns CD's anymore and maybe is going out also in reading DVDs, but I'm not sure cause I've not tested it yet... (I'm getting crazy to buy a new drive, a Super one, but here in Brazil the ones for the mini are to expensive ).

Hope to get some help!