how to I fix with the disk utility? or dvd?
I am not sure how to go about it.
The only thing that really scares me is I don't have a large enough external to save all my data. I have been meaning to buy one, but never did.
Try to repair your Macintosh HD via Disk Utility started from the restore or installation DVD.
Mac OS X - Using Disk Utility to Repair a Disk
what is "fsk"