I erased my OS

and I bought system software on eBay but the disk was unlocked. The software download was almost complete and the mac installed files over the operating system. Now I am back to where I started. How can I get this $10.00 PowerBook to work? I have an Aluminum PowerBook 15 inch and love it. I do not NEED my 170 to work, but I want to give it to a kid I know. Thanks.
