Spinning Beach Ball - No Hard Drive


I have G4 Power Mac, running OSX version 10.3. My technical expertise is not great, so please be as simple as you can!

After the weekend, in which a visitor used the 'visitor' user account, I now cannot access my own account. the 'visitor' account is all right. Not sure if the two events are connected.
The beach ball keeps spinning. No hard drive or folders appear on the desktop. The Finder menu does not work, but the volume etc on the right hand side does. I can access all programmes on the dock, except Word, which has developed a question mark.
I have tried starting with the external hard drive and the modem out. I have taken the plug out of the wall. I have started up with my Install Disc 1 (Version 10.2).
I have never done a 'repair permissions' as I didn't know about it, but can't get in to do that now, which I see recommended for spinning beach balls. This option isn't available to me, unless there is some way I can access it from the 'visitor' account, which of course I don't have permissions to do.

Hope you can help!

Thanking you in anticipation.

I folowed the instructions for fsck, but no luck.
I managed to start in 'safe mode' and then change the permissions on the 'Visitor' account. The Visitor account was OK. From there I repaired persmissions. I switched off and returned, still no hard drive. I went back in to the Visitor account and this time I logged out and logged in instead of switching off, and lo and behold, the hard drive popped back again!