Hi Jed,
Thanks for getting back to us; that's pretty much what I suspected, but it's best to err on the side of politeness rather than slam someone who doesn't know about the dual-pitfalls of encryption and compress on Windows volumes. Hopefully, you didn't have additional secondary drives, internal or external USB plugged into your computer when the W10 AU update came into your machine. That's bad news for sure. And now with the advent of new Ransomware viruses such as Nemucod and Crytpolocker, you shouldn't have extra drives plugged into your computer as the viruses can lock up your Windows and all your files
ON ALL YOUR CONNECTED DRIVES AS WELL!! 
I just spent about the worst 4 weeks ever fixing a Customer's computer that was locked with 20 years worth of his business and personal pictures on his computer and all his external backup drives too.
You should only connect those drives to your computer, when you are performing backups, and then immediately disconnect them. Another thing I do, and sometimes I forget this too, is you should
DISCONNECT ALL YOUR BACKUP DRIVES on Monday the day before the weekly W10 AU push updates (Tuesdays) are coming into your computer from Microsoft. This is true, even if you've attempted to turn off all the Windows Update settings as well as
WUDO. Here's a discussion for you to read further on that:
How do I turn off automatic driver update in Windows 10 AU Also, too, there are now new viruses out there that specifically will turn on bitlocker encryption or even compression on your bootdrive volume, so when you said you didn't turn it on because you didn't want or need it; that's very likely.
That means that if you didn't do it intentionally, and you don't share your computer with friends or family-members or roommates, you could have one of these little nasties in your computer which turned on bitlocker without your knowledge or consent.
Did you try running your antivirus and scan/remove all viruses found? If not, you should do so before the rebuild of your W10 system. Additionally, you should download the free
MALWAREBYTES antispyware from
piriform.com and scan/remove all spyware viruses detected.
Finally, if any of your secondary or external drives are found to also have bitlocker enabled on them, you may need to do a good virus scan/removal on each of those drives as well prior to reinstalling your W10. If you don't, as soon as you plug in one of those infected drives to your newly installed W10 bootdrive, that virus could re-enable the bitlocker on your bootdrive, and you'd be right back to where you are now!!
I hope some of this information proves useful to you.
Cheers!
<<<BBJ>>>
