I'm assuming the disks themselves are known to be working? Odds are good that the drives are dirty from years in storage rather than broken. Start by running a cleaning disk through them a couple of times (a kit like
this). Hopefully that will free them up, but you may have to pop the lid off the drives themselves to clean some of the mechanical components with a q-tip/cotton bud. Isopropyl alcohol is the cleaner of choice for such an operation.
