Your iMac G5 supports 10.5 retail installer which is available by calling the Apple Store online often. Other places which may have it, you have to make sure that you actually get the retail disc which looks like
*
and does not say upgrade, dropin, or OEM.
The only thing about the retail installer is that it does not:
1. Include Classic.
2. Include Appleworks.
3. Include the hardware test.
4. Include the games that came with the Mac, except Chess.
5. Include iLife, except iTunes, unless you get the Mac Box Set.
You might be able to obtain the original discs from a user who has the same Mac model at a usergroup:
http://www.apple.com/usergroups/
being aware of the license restrictions of the software.
Naturally you could use it to run the hardware test, or test the operating system on your Mac using the Disk Utility if it never was updated.
Note, the Disk Utility check can also be duplicated simply by using Single User Mode:
http://support.apple.com/kb/TS1417
Using fsck if necessary
section applies when you don't have the original discs. This doesn't do a hardware test, but does do a rudimentary directory test and repair. For more sophisticated directory repair, go and get Alsoft Disk Warrior.
Before doing any extensive repair, be sure your data is backed up*:
http://www.macmaps.com/backup.html
- * Links to my pages may give me compensation.
Message was edited by: a brody