If the 10.4 DVD has a gray color & it's from another model Mac, it won't boot. Some how the Mac may have been "fooled" the first time.
Can you describe the "crash"?
Try inserting the DVD in the disc drive while the Mac is not running. Then startup while depressing the Option key. Does the 10.4 DVD show up as one of the sources to boot from?
Will it boot in Safe Mode? See
What is Safe Boot, Safe Mode? (Mac OS X)http://docs.info.apple.com/article.html?artnum=107392Takes a while to run, but it usually "fixes" problems.
Doesn't your GF have the restore DVDs that came with the PB G4?
Cheers, Tom
