(quoted from post at 05:34:40 10/23/14) You probably had Cryptolocker on your computer. There is no cure for this after it encrypts your files except paying ransom. If you have a backup drive hooked to your computer it will also encrypt it.
Explanation of Cryptolocker
This looks like it might be it by the description. And there is no way to get data back if this is what happened, it's very sneaky. But, if you do pay them the high amount they ask, they actually do get your data back. So they are "good" bad guys, but only because they know if they didn't give the data back, people wouldn't pay. The data is actually lost, as they encrypt it on your computer, no way to hack it to get it back without their key.
If it was not this, then there is an easy way to get data back by moving the drive to another computer, or using a Linux live disk. Just boot off of the cd or usb drive and copy the data to a usb stick, disk burner, or other usb type drive. Very easy and works well.
I use Linux too as my only system, Windows gets used only to help walk people through stuff. I've been the area "tech" for years and fixed a number of systems. For my personal system, nice to have something that just works without all the antivirus, scanning, and thinking about stuff that a Windows system requires. Something that "just works" is nice.
Free antivirus is good enough. Or get something when on sale, there's usually one of the main ones that's free after rebate if you look, every year. I recommend Panda Cloud free, it topped the testing charts of the free ones last I looked, detected the best, it's been around for a long time if you've never heard of it. If you pay for something, Malwarebytes would be where to put it, you can get a lifetime license for less than $20. Also, install Malwarebytes anti-exploit in addition to regular Malwarebytes, and Microsoft EMET. And use about anything other than Internet Explorer, and don't open email attachments if you don't have to. With the web browsers, Chrome or Firefox, install adblock and noscript at least.