Could the HD maybe be dead? You should try another.
The way it is installed internally, it is difficult to make that mistake: the CD slots in to a special connector with adaptors, while the HD is installed directly with the ribbon cable not he front of the computer.Yep definitely sounds like the HD is causing the trouble. The 6360 uses a standard IDE hard drive so replacing it will be easy enough. Any old IDE PC hard drive will do the trick.
Watch out as there is both an IDE and a SCSI interface in the 6xxx series machines. The CD ROM uses SCSI whilst the hard drive uses IDE so be careful which one plugs in where.