My main comment is that these ransomware type threats are genuine so don't ignore them.
My son had one on his PC a few months ago which basically locked him out of his PC.
Every time he started up his PC he got this image (said to be from the FBI) that totally blocked out his screen. He could not get past it to his Windows desktop so he could not do anything.
Luckily I am fairly experienced on PCs so I download the Kaspersky Rescue disk (for free), booted his PC up using it, and it ran a virus scan and got rid of it.
For people who are not that experienced it cold cost you £50 to get a PC engineer in to fix it.
1) Create a "spare" Windows logon on your computer that you don't normally use. Then if your main Windows userid is locked out you may be able to log on to the spare one to run your security software. Creating a spare Windows account is easy if you go into the Windows control panel and select User accounts.
2) Make sure you have security software on your PC and run it regularly.
3) Make sure you download all Windows and Office updates as soon as you can (or set it on automatic).
4) Backup ALL personal files to one or more external hard drives. You can buy an external hard drive for £50 or so. Just plug it in to your USB port and copy personal files from the PC to the external hard drive.
If you have a spare PC in the house, consider copying your personal files to that as well. I always say one backup is never enough as any backup can fail for one reason or another.
5) Remember as Christmas comes more spam and scam types emails are sent out.
Be wary of any emails that link to "funny" Christmas cards or videos, as they could just be links to a virus.
And if you get emails saying "Be aware of this scam, pass this email to all your friends" then PLEASE don't forward the email to all your friends.
Often these type of emails are the scam in themselves are often the "scam" they are reporting is in fact NOT a scam at all.
Don't assume these sort of things cant happen to you, it can happen to any of us.