Microsoft Security update https://technet.microsoft.com/en-us/library/security/ms17-010.aspx
Ms Defender Includes some ransomware protection Ensure updates are on regardless of Windows updates settings.
Protection: Malwarebytes Anti-Ransomware (Free) http://www.bleepingcomputer.com/download/malwarebytes-anti-ransomware/
Virus Checker: Avast! Free  (or AVG Free) avast!    
Recovery Help

Analysis after attack to assist in recovery

I suggest you download this and burn to a CD/DVD for future use.

https://www.nomoreransom.org/
Malware scanner: MalwareBytes Free MalwareBytes
Recovery: Farbar Recovery Scan Tool (Free but donation option)I suggest you download this and burn to a CD/DVD for future use. www.geekstogo.com
XP recovery: Finds encryption key Only works if the infected PC has not been re-booted https://github.com/aguinet/wannakey
Other useful safe links... downloads.cnet.com
bleepingcomputer.com
Back up your data frequently Use a USB external hard drive and a backup prog such as Windows Backup Always unplug the hard drive after backup completes.


RANSOMWARE PROTECTION & RECOVERY LINKS