PPC roadmap. Should I buy 10.4 or 10.5 - and where to get it second hand

Question

My hard disk has decided to start giving notice, but luckily I have managed to get my data off.
The grey 10.4.2 reinstall disk supplied by the reseller is not letting me reinstall:
alert "this software cannot be installed on this computer"
This I take to mean it a customised build specific to the hardware - and does not match my configuration.
So I am stuck.
Q1 Do I demand the correct version (any version that works!) from the retailer - and what are my rights (in New Zealand - and elsewhere?)
Q2 Is it legal to purchase a second-hand OS disk (assuming the original computer it is from is no longer working).
Q3 If OSX 10.4/5 is no longer for sale from Apple - is it still supported (I see a lot of support on the forums) which is good.
Q4 [Embarrassed] How do I get the disk1 CD/DVD to eject (the only options are to Restart or Cancel). And there is no emergency eject hole to push a paper clip in that I can see!
Yes, I have formatted the disk HFS Journaled as required using the disk utility.

Answer 1

Welcome to Apple Discussions!
Determine the age of your iMac G5 by reading its serial number.
xxABCxxxx is the standard form of a serial number, where only the ABC values matter as far as determining the age of the machine (x means it can be any value). A is the year, and BC are the week of the year. Use a spreadsheet with cells adding up 1/1/year with 7 in consecutive rows to determine the week by reading the row number and then the matching date. Once you have the matching date, you can determine which version of 10.4 will run on your Mac. You might even be able to call AppleCare if you bought the machine from an authorized reseller and ask for replacement original installation discs, if you lost them. If you bought from a non-authorized reseller, contact them and ask for the original discs, they aren't their's to keep. Use Wikipedia to match the version of Mac OS X with the date found in the serial number. A
serial number for instance of xx540xxxx would mean it came out October 1st through October 7th 2005. According to:
http://en.wikipedia.org/wiki/MacOS_X10.4
That falls before 10.4.3's release, but after 10.4.2's release. That means that the 10.4.3 retail from October 31, 2005 would work with your machine, but not 10.4.2 retail or earlier. 10.4 retail of any version looks like * and 10.5 retail of any version looks like * and neither says Upgrade, OEM, or DropIn on the disk, but the specific 10.4.x and 10.5.x release is written in fine print on the disc.
Before upgrading, follow these steps*:
http://www.macmaps.com/upgradefaq.html
See this article how to eject without a paperclip, and without an operating system:
http://support.apple.com/kb/HT2179
Note this article was down the last I checked, though I'm going to ask a moderator put it back up.
- * Links to my pages may give me compensation.