Ways to Protect Your System
1. Setup a backup of your data using tools built into Windows or a free or paid backup program or online service. I like Acronis and Macrium Reflect for backing up my system. Follow the 3-2-1 backup rule. Have backups on 2 different types of medium locally and 1 backup offsite like Carbonite or Idrive. The local backups can be to a USB drive, External Hard drive or other medium.
2. Setup a standard user account instead of using an administrator account. If an virus gets into your system they will have full access to everything because you are using an administrator account.
3. Install a good Antivirus program like AVAST, AVG, Bitdefender, Kaspersky, Avira, Trend Micro, Panda, Eset or others. The free version of AVAST is here.
4. Install a good firewall like Zonealarm. The free version of Zonealarm is here. Some antivirus products include a firewall so check whichever anti-ivrus you are using to see if it has a firewall. Firewalls and anti-virus programs will turn off the Windows anti-virus or firewall during installation.
5. Install a second software for malware prevention. Be careful not to install 2 antiviruses as they will cancel each other out. ( good examples that won't conflict are: Malwarebytes, HitmanPro, Spybot Search and Destroy, Adaware)
Malwarebytes Premium 3.0 also helps prevent ransomeware and rootkits.
6. Restrict certain file attachments like .exe or executable files. Depends on the email program you are using. Don't open attachments from people you don't know. Sometimes viruses send out emails from computers and you think it is a friend, but it's not. This is a very common way people get infected.
7. Don't click on links in email. If you need to check your accounts then go direclty to the website. The linksin email may be phishing links which may all the bad guys to access your computer or change your passwords or infect you.
8. Show file extensions. This helps you identify file types so that you don't accidentally click on a bad file and get infected.
9. Keep your software and Windows updated with the latest security patches. Patchmypc and AVAST will allow you to update applications on your computer. Do your Windows updates.
10. Use a web browser add-on like Bitdefender TrafficLight, AVAST Online Security, NoScript Security Suite, Avira Browser Safety.
11. Don't allow people who call you randomly to access your computer. They are probably the ones that infected you in the first place and they are trying to get money out of you. They say they will fix your computer, but they may lock you out completely.
Here is a good video from Britec