Hi Coppendriver.
Don't put in any OS higher then 14.9 in there. Since it is a G4 Power processor it is not going to work beyond that. 512 MB is much to low for this machine. It supports DDR2 memory up to 2GB.
• The PowerBook G4 (17-inch Double-Layer SD), only, uses PC4200 DDR2 SDRAM
SO-DIMMs, with a maximum height of 1.25-inch (30 mm).
• The PowerBook G4 17-inch series uses PC2700 (also called DDR333) DDR
SDRAM SO-DIMMs with a maximum height of 1.25-inch (30 mm).
(go with the mouse over the Apple in the left top corner, choose "about this mac" from the pulldown menu, It shows you a window that tells you what kind of memory kind is used in yours.)
Re-installing the OS won't do much good, and certainly you don't have to change the hard drive. Those are solutions for a windows environment.
There is a application on board your macbook called disk-utility, you find it via the search on your disk (press ⌘f), here you can restore owners-rights and clean up your disk. Choose the "control and repair" option for your hard disk. It takes a minute or two. (do this once a month or so)
Don't worry about defragmentation on a Mac. It takes care of that itself.
The nice aspect of your macbook is that it can also run the old apple programs in "classic mode", nice extra, but if you don't use it, be sure it is turned of since it is memory-consuming, you do this by going with the mouse over the Apple in the left top corner, choose system-preferences, choose "classic" and put the switch on off.
Always keep minimal 10% of space free on your hard disk. In your case that would be 12.8 gigs.
Keep your desktop empty of heavy data. Drag it to your hard disk and (if you want) leave just an alias.
Sorry, i didn't catch this topic early-er. if you want I can sent you the service manual for your machine. It is 19,8 mb big so I can send it to you by wetransfer if you sent me a Email address.
greetz
Frank