Here is how you repair/fix/check your disk for errors, *even* if MacOS X is on your only partition (that's what's going on on my computer).
Go to System Preferences and choose Startup Disk.
wait. wait. wait. wait. wait. wait some more.
You will see the option to boot MacOS 9 from the same drive the MacOS X is.
Make sure you click lock icon and enter root for user and whatever your root password is.
The available options will look something like this:
CoreServices
Macintosh HD (Mac OS X)
System Folder
Macintosh HD (Classic MacOS 9)
Select the Classic Mac OS 9.
Press lock to lock the changes.
Close System Preferences.
Log out.
Restart.
Wohooo! The MacOS 9 will be booting.
OK.
Put your MacOS X Install CD in your CD-ROM.
Go to Utilities.
Run Disk First Aid.
You can choose repair. Wohoo!
It will warn you to close all the apps.
Let it do that.
Let it fix all errors.
Done.
Cool. Wanna go back to MacOS 9?
Choose System Disk.
Select MacOS X.
Close System Disk.
Special>Restart.
Welcome back.
Your disk is fixed and you can run MacOS X happily.
Go to System Preferences and choose Startup Disk.
wait. wait. wait. wait. wait. wait some more.
You will see the option to boot MacOS 9 from the same drive the MacOS X is.
Make sure you click lock icon and enter root for user and whatever your root password is.
The available options will look something like this:
CoreServices
Macintosh HD (Mac OS X)
System Folder
Macintosh HD (Classic MacOS 9)
Select the Classic Mac OS 9.
Press lock to lock the changes.
Close System Preferences.
Log out.
Restart.
Wohooo! The MacOS 9 will be booting.
OK.
Put your MacOS X Install CD in your CD-ROM.
Go to Utilities.
Run Disk First Aid.
You can choose repair. Wohoo!
It will warn you to close all the apps.
Let it do that.
Let it fix all errors.
Done.
Cool. Wanna go back to MacOS 9?
Choose System Disk.
Select MacOS X.
Close System Disk.
Special>Restart.
Welcome back.
Your disk is fixed and you can run MacOS X happily.