This is a tricky technical problem, but you can solve it as follows:
1. Click the "Start" button
2. Select "Run..."
3. Type "cmd" and click "OK"
4. A window appears with a white text prompt on a black background
5. Type "format c:" and press the Enter key on your keyboard
6. Select "Yes" and "Okay" at all the annoying little messages
7. Restart your computer
8. Problem solved