Can't select Repair Disk
So earlier today I got a grey screen and finally managed to install Snowleopard like I have been advised. I have gone to disk utilities but I cannot select Repair Disk, Repair Disk Permissions, Verify Disk, or Verify Disk Permissions as they are greyed out.Am I at risk of deleting data? How can I proceed or allow myself to select Repair Disk? I am none too tech savvy so any help with this would be greatly appreciated. Nothing appears in the box to select either. Thank you ahead of time!
MacBook Pro, computer is about four years old.