Experienced this recently with a user at work - it was a fake av scam. Yes, you'll want to backup your data to an external source. Then, you'll want to attempt to use system restore to go to a previous restore point. At that point, run an antimalware scan (malware bytes, superantispyware, etc.). Let it quarantine anything it finds.
If you feel you're still experiencing complications at that point, I would reload your OS entirely.