Can you boot into Safe Mode? Click here to see how
If not then you need to boot to WinRE and run chkdsk from a command prompt:
- Tap F8 during startup to get to the Startup Options menu.
- Choose Repair Windows.
- After choosing the location and logging on, click on the Command Prompt option.
- Type the following command followed by the ENTER key:
CHKDSK C: /F
Let CHKDSK run to completion. It may take some time so be patient and do not restart the computer while it is running.
When CHKDSK has completed, restart and see if you can get into normal and/or safe mode.