how do I set my HD to be case-sensitive
This is the inverse of this solution on superuser.

The easiest way is to use a tool like Carbon Copy Cloner, clone the volume to an external drive, format your drive as case sensitive and restore it back. As this inverse question "Can CCC backup a case sensitive volume and restore to a case insensitive volume?" and answer on the CCC forums describes:


  Yes, that should work fine. I just did a quick "backup bouncer" test with this scenario (10.6.2) and it worked great. The only potential issue is if you had some items with the same name, differing only in case, in the same directory. Only one of them would be copied over to the case-insensitive filesystem. For example:
  
  /Users/david/Desktop/Files
  /Users/david/Desktop/files
  
  You could have both those folders on a case sensitive filesystem, but the last item to be copied to a case insensitive filesystem would overwrite the previous item with the same name, different case. I really doubt that you've created such a scenario yourself, and the OS certainly doesn't do it for the standard installation, so I would be too concerned about this. Clone away, it should work great.
  
  Mike


The other solution is to experiment with this older HFS Converter tool. Have a backup before you attempt this.