Losing power while synching new music shouldn't fully corrupt the hard drives. The worst it should do is to corrupt the database and put you in this situation
However, we all know there's sometimes a big distance between "should" and "did", so if your hard disks really did get corrupted, then there are other repair steps we can take, depending on the nature of the corruption.
Can you, in more detail, describe exactly what happens to the player now? If it's just the long "building music databases" thing at the link above, then all is well and that link contains your repair procedure.
If it's something worse, give us more details about what's going wrong and we can work from there.