It will be worthwhile to get a set of install/restore disks. They will help you track down whether it is the system or the hard disk; and either way you will need to install a new system. If you need to go to a new HD here are 2 links with info on how to do a replacement: for the original, CD tray-loading models - http://www.djonmac.com/index.html and for the slot-loading - http://www.appletalk.com.au/forums/i...?showtopic=436.
Good Luck.
Badger