Reinstallation Problem

[CollidedMoon]

Hello everyone !
My sister's MBP started to have problems, it was stuck on the Apple logo and she had to reset the PRAM to boot it. Some apps also had a "?" and were not able to start and she couldn't download anything from Firefox. I thought it was a virus, so I decided to format the HD using another MBP. I also made a Mountain Lion bootable USB with this video. I tried installing Mountain Lion on the MBP and the bootable USB worked, but when the computer tried restarting, it blocked on the apple logo again. I verified the HD using Cmd + R and it is fine. I don't think it's a RAM problem, as I replaced the RAM with the other MBP I have (which works great) and it still had the same problem. Help !

 

[Cory Cooper]

Hello and welcome.

-What exact model is the MacBook Pro?
-The prohibitive sign means it can't find a valid System Folder on the startup disk. Maybe the install didn't complete properly?
-Disk Utility only verifies the catalog file on the hard drive, not the entire surface. You would need a utility like Drive Genius or Techtool Pro to verify the integrity of the entire drive by performing a complete surface scan.
-Did you try a PRAM reset at any point?
-Does the MBP boot into Safe Mode (hold the Shift key during startup until you see the Apple logo)?

C