|Try to start Windows in "Safe Mode" by tapping F8 as soon as you turn it on.|
F8 should bring you to the Advanced Boot Options screen.
Use up/down arrow keys to highlight "Safe Mode", then press Enter.
If Windows manages to start in Safe Mode, perform a disk error check:
Right-click the C: drive icon and choose "Properties".
Click the "Tools" tab
Click "Check now"
Tick both boxes.
Click "Schedule disk check"
If that doesn't work and you need more help, please mention what you've already tried so we don't ask you try something you've tried already.