Sometimes if the a crash happens on your windows your profile get's damaged.
You desktop files and all settings are missing and you appear to be in a totally new profile.
Most cases I experienced can be solved simply.
Here is my solution:
- Open My Computer
- On your system installation (usually C:) right click and select properties.
- Click on Tools Tab
- Click on error checking button
- Select option Automatically fix file system errors
- You will be prompted to run this maintenance at next reboot. Click ok
- Reboot