Power Mac G4

Tiger 10.4.11 I think but I saw you could get Leopard to work on it:

http://www.engadget.com/2007/10/26/leopard-on-an-8-year-old-g4-power-mac-can-it- be-done/

No download, free or for $.

Tiger install DVDs are in short supply. Tiger is no longer available at the Apple Store but may be available for $129 by calling Apple Phone Sales @ 1-800-MY-APPLE (1-800-692-7753). For other sources, do a Google search for MA453Z/A (10.4.6), MA190Z/A (10.4.3) and M9639Z/A (10.4) . Also look on eBay. Be sure & buy a retail version (black with silver X) and not a model specific version (gray) (See Can I use another Mac's system restore disc on my Mac? ). Expect to pay (possibly a lot) more than the Apple list price of $129.

Also check these web stores: http://www.lacomputercompany.com/cgi-bin/rpcart/index.cgi?command=dispitem&type= sku&sku=19521 http://www.allmac.com/shop/index.php?cPath=5_10003

Possible Alternative if you are currently using Panther 10.3 – Do a Google search for Tiger 10.4 Upgrade DVD . It will upgrade your 10.3 to 10.4, but it doesn’t contain the full retail Tiger installer. Should be cheaper than the retail Tiger install DVD.

After you install the base 10.4.x, update to the final Tiger version 10.4.11. Here's the link for the 10.4.11 combo update http://support.apple.com/kb/TA24901?viewlocale=en_US

Look at this link Mac OS X v10.4 Tiger Installing Software Support Page
http://www.apple.com/support/tiger/install/

You can also download the Tiger Installation and Setup Guide
http://manuals.info.apple.com/en/TigerInstall_SetupGuide.pdf

When you upgrade the OS, do it via Archive & Install. See About the Archive and Install feature http://support.apple.com/kb/HT1710
Be sure to select Preserve Users & Settings. Also, repair permissions before and after the install.

 Cheers, Tom 😉

Mac OS X Installer DVDs are a crucial source of stand-alone Utilities for Hard Drive Repair and a few other debugging and maintenance functions. When booted from the DVD, your Hard Drive can be examined in detail and freely Repaired without fear of crashing the running System.

Genuine Apple Mac OS X 10.4 DVD is also essential:

HT2648- Only use Mac OS X 10.4-compatible disk utilities with Mac OS X 10.4 volumes

overclock that 400mhz cpu

There are a few software cheats to get around the 867 MHz check in the 10.5 Leopard installer.

As for overclocking, you may get 5 to 10 percent additional if you are extremely lucky, but you will never get it up to 867MHz by overclocking. Forgetaboutit.