PowerPC :: IBookG4 - Applications Not Opening

I've been given an iBook G4 1.33Ghz 512mb Ram Notebook to repair. The problems seem to be that only a couple of the applications work...the desktop fires up OK. But I can only fire-up Safari..When you double click any other app, they jump up and down, but nothing happens. I was going to format and reinstall everything, but how do I get the required files off the iBook, I can't see any icons on the desktop to be able to "open" the HD to remove & copy files....Within the OS the CD-Rom doesn't mount either....nor any USB Stick as far as I tell, I was thinking of buying an External HD & Trying to install the MAC OS onto it & remove the files from the Internal HD afterwards, Is that feasible.