Your machine is infected and your have this screen:
- Don't pay - Research suggests that payment will get your files back two thirds of the time
- Re-install your operating system - remembering to patch it!
- Create a standard user account for general use, and keep the administrator account for configuration changes only.
- Install a good malware protection solution, and update it
- Scan your machine with your newly installed and updated malware protection software.
- Re-install essential applications, remembering to check for patches, and switch on auto updates.
- Copy back data from backups, remembering to scan it as you do. One of your backup files could be infected.
- Be mindful of any email attachments or links within emails
- Continue to update malware protection, operating system and applications
- Ensure backups are happening to prevent data loss, and even consider multiple backup destinations
- Only use the admin account for configuration changes
This advice is more based for home users, but your can see the relevance to organisations as well. For a more detailed look at ransomware, and what approach a organisation can take, have a look here.