New
#11
Have you checked the disk? If there is a problem with the disk, a new one is needed.
Either way,
I would copy any important data somewhere safe - to an external disk, or even a usb disk if necessary. Also back up your activation somewhere safe. SEE HERE
Then go for a clean reinstall. I have done it countless times. Takes a little time to get the updates and restore activation, copy data back, etc.
You will probably be surprised at how much snappier a clean reinstall is.
Quote