Remove (or Highlight) name duplicates?

Is there a way to highlight, or even eliminate, duplicate names from a sheet (without having to do a specific search for a name)?

I know it should be relatively easy to find this information, but I am trying to run so many reports, I don't have time to do the research.

For example, this registration sheet is for an event. I want to be able to do a quick "Countif" to determine how many people are registered, without having to weed through the sheet for duplicate names (Anne Austin, for example).

Is there a formula I can input that will pair down duplicates to a single entry so my counts are accurate, very quickly? I have to update a spread sheet with information from an online database. The way the reports are set up in the online database isn't as quick and efficient as I need it to be when converted to Excel.

Thanks,
J