Cryptolocker has been rearing its ugly head lately and it is probably one of the worst viruses out there because it hijacks your data with encryption and then charges you $400 to remove the encryption.
Some antivirus programs are powerless to stop this infection. In most cases, infections seem to be caused by viruses embedded in email links or attachments. As always, please be careful when opening email, even if it is seemingly sent from one of your contacts. It is always best to write the person directly and ask them if they intended to send you the email before opening it. Learn to recognize the signs of fake emails (misspellings, weird capitalization, strange grammar, etc.).
But there is even more hope. A brilliant coder decided to build a tool that will patch any version of windows against this virus for free. You can download it and find out more at the following link.
https://www.foolishit.com/vb6-projects/cryptoprevent/
Let us know if you have any questions.