Phew, ok seems to be fixed now. I had to plug into the computer and hold the on/off button constantly until the computer registered the device, then was able to go in through Explorer and remove the corrupt file/s, basically everything I added today just in case.
Big thanks to this thread!
https://www.mobileread.com/forums/showthread.php?t=78891
So relieved! I love love love my reader!