Is there a free program, other than the Apple Hardware Test, that I can use to help pinpoint possible hardware problems with a G4 Quicksilver MAC?

I have been running AHT non-stop on this machine for hours without a problem, yet I can't install the OS without error. I've tried 10.2, 10.3 and 10.4 install discs.

I've detailed my trouble in the OSX forum.