I reset my PRAM & NVRAM and tried going back to Snow Leopard with no luck. I put in my install DVD and ran Disk Utility from there and got this result:
Verifying volume “Hard Disk Drive”
Checking file systemChecking Journaled HFS Plus volume.
Checking extents overflow file.
Checking catalog file.
Incorrect number of thread records
Checking multi-linked files.
Checking catalog hierarchy.
Checking extended attributes file.
Checking volume bitmap.
Checking volume information.
The volume Hard Disk Drive was found corrupt and needs to be repaired.
Error: This disk needs to be repaired. Click Repair Disk.
Verify and Repair volume “Hard Disk Drive”
Checking file systemChecking Journaled HFS Plus volume.
Checking extents overflow file.
Checking catalog file.
Incorrect number of thread records
Checking multi-linked files.
Checking catalog hierarchy.
Checking extended attributes file.
Checking volume bitmap.
Checking volume information.
Repairing volume.
Rechecking volume.
Checking Journaled HFS Plus volume.
Checking extents overflow file.
Checking catalog file.
Incorrect number of thread records
Checking multi-linked files.
Checking catalog hierarchy.
Checking extended attributes file.
Checking volume bitmap.
Checking volume information.
Repairing volume.
Rechecking volume.
Checking Journaled HFS Plus volume.
Checking extents overflow file.
Checking catalog file.
Incorrect number of thread records
Checking multi-linked files.
Checking catalog hierarchy.
Checking extended attributes file.
Checking volume bitmap.
Checking volume information.
Repairing volume.
Rechecking volume.
Checking Journaled HFS Plus volume.
Checking extents overflow file.
Checking catalog file.
Incorrect number of thread records
Checking multi-linked files.
Checking catalog hierarchy.
Checking extended attributes file.
Checking volume bitmap.
Checking volume information.
The volume Hard Disk Drive could not be repaired after 3 attempts.
Still not sure how to fix this. :/