There are some encryption viruses that have been helped to unencrypt the system. The one that comes to mind is the autolocky virus. Unfortunately there are plenty of others with no answers or help. The only thing you can do is protect your data before this happens. Here are a few things below that may help.
- Use an external back up hard drive of at least 1 to 2 tb
- Only have the back up drive connected while the back up is running
- Back up your data to the cloud with something such as carbonite
- Create a standard profile and copy data to it.
- Ransomware Viruses usually go after administrator accounts
- Have a back up computer just in case your computer gets hit and goes down