Some people use MacMedic.

I don't, I heard it was evil. The company treated Mac users really badly concerning service. There were a couple of websites detailing how they refused to support the people that bought their app. Their app actually torched some drives.

I wrote them after seeing these reports, and the WEBMASTER wrote me back and he was really snotty and nasty to me. So I wrote MacMedic off and never would try it. If you do a search for "MacMedic" on Macfixit or Macintouch you will find additional claims about Total Recall.