If you can boot into safe mode and it looks ok, your problem is most likely caused by a software problem.
Rather than go through all the normal fixit steps for osx, it might be just as easy to reinstall the system via anArchive and Install (preserving all settings, etc.). You can read more about archive and install in Help. You do an archive and install by going to Options on the osx installer, but read up on it first. Before install an os, make sure to run disk utility and repair the HD from the installer disk. You will also find Hardware test on the installer cd/dvd. You can run that to see if it reports andy hardware problems.
As for various drives, Open disk utility and see if the various drives show up in the left pane. If not, Click on mac hard drive in the left pane and then hit the Repair Permission button and see if that helps. If you're plugging in an external HD, you'll have ot format it for mac. Clcik on it in the left pane of disk utility and then clcik the Erase button. Select Mac os extended, journaled as the format. The mac should recognize the drive after that.
Using OSX 10.3.9 on a G4 & G5