Ransomware is a new trend in malware. It comes in various forms; but, surviving it or recovering from it usually requires a backup. The best defense is prevention and a bit of basic knowledge on the part of the user. No, Microsoft will not call you under any circumstances; The FBI will not hack into your computer to tell you your machine is doing questionable things, and any time some weird popup tells you that you have viruses or malware on your computer, you do and it includes that popup. Prevention amounts to keeping your anti-virus up to date and running regular scans combined with keeping your anti-malware similarly up to date and running regular (weekly preferred) scans. If you are using Windows Defender (windows 10) or Security Essentials with Defender (windows 7 and 8) you have the basic tools installed, just keep them up to date. Other vendors (McAfee, Norton, TrendMicro, etc.) have appropriate suites that will similarly protect you (Sophos and Vipre have suites for large businesses that are quite impressive in scope and protection level but usually cost prohibitive for home users).
Even so, any of us can make the fateful mis-click or have the bad luck of going to a hacked website that starts up the infection. If it slips past your anti-virus you could be in a situation where a reboot will correct the issue (lucky you) or where restoring all of your data from backups is necessary, or even restoring the machine to factory fresh state and then restoring all data from backups. My best advice is to call someone experienced before you mess with it; but, if you feel up to the challenge, update all anti-virus & malware products, scan completely, verify that the bug(s) are gone and restore lost data (or all data) from backups.
If I seem like a broken record about backups, that is fine with me; backups are that important. You should have many, starting with previous versions (windows 10), synched with a cloud service, AND detachable hard drive / thumb drive, etc. The detachable part is important because some of the current malware or ransomware will mess up your cloud files also or you’re synched files if the synch is to some place that is available when you get infected. Therefore, if it is important, have a copy on removed media!
As a last note, remember you can’t inherit from a non existent dead relative or win an African lottery that you didn’t enter; delete emails suggesting you have with extreme prejudice and do not open any attachments or visit their websites. I guarantee that bad things will happen if you follow the links or open the attachments.