Originally posted by strider42
go to the startup disk control panel and select your hard drive. incidentally, zapping the pram can potentially cause this problem. I'm assuming with these instructions you are running OS 9. i don't know the procedure in OS X, but I imagine its more or less the same.
its a good idea to run a good disk utility (or at least disk first aid) just to make sure you don't have any directory corruption which could be causing issues.