Thor is essentially the latest iteration of Locky Ransomware—which means you’ve hit a serious snag. You might be able to recover if you had a recent backup or a system restore point active... allowing you to roll everything back to how it was before the infection. I would suggest downloading
http://www.shadowexplorer.com/downloads.html to see if any restore points are actually available. It will tell you if there is a way back. If not... then you're likely out of luck.
The Ransomware likely triggered because you opened a specific file containing Thor—it then proceeds to lock down every file with a matching extension. If you can identify which file caused this (a zip, a txt, etc.), simply deleting that original file might help.
If you aren't certain which file was the culprit, there is an open-source tool called MBRFilter that can block Ransomware (http://www.bleepingcomputer.com/news...r-boot-record/); you can find it on GitHub and install it fairly easily... if you feel up to it.
