If you have the Tiger version of Mac OS X, I would strongly suggest not using OnyX.

Both times I tried to use, it effed up my computer, giving me an error and "invalid node structure" every time I ran Disk Utility.

The first time, I had to wipe everything off my computer and start clean.

This time, I'm trying to get Disk Warrior and see if it can do anything. I don't feel like losing all of my stuff again, thanks.