This reminds me that the dvd drive of our desktop is not functioning well. If something goes wrong with the OS, it would be a big problem. Now this issue - to have the dvd drive replaced. It is expensive so a used drive is recommended for lesser expense. Let me think about it for now. I'm still on a holiday.
Always have an repair disk setup and ready. IF the OS starts going off and not acting right then you use the recovery and repair disk that repairs or finds what the error is and it will replace the bracken files without the need to install and full OS again