In Startup Repair select the Command Prompt option.
Type "chkdsk /r" (without the quotes) and press Enter
If it asks to reboot, tell it OK and let it reboot.
chkdsk /r will run and you'll see the results on the screen.
If that doesn't fix it, then try this:
I suggest starting all troubleshooting with the following diagnostic tests. They'll save you a lot of time and heartache if there is a hardware failure, and you'll have the disks on hand in case you need them in the future:
Please start by running these bootable
hardware diagnostics: Memory Diagnostics
(read the details at the link) HD Diagnostic
(read the details at the link)