Strange files and folders created at every startup

I have several folders and files that appear on my drive at every startup. The folder and file names are seemingly random words and numbers, and the files are of several different types (rtf, jpg, sql, etc.), although the combination of types is the same in each folder, and there are always 10 files in each folder. I can delete them, but they re-appear in minutes, in the same place but with different names, all with exactly the same creation time. After a restart, all the files and folders have new names and are time stamped for the time of startup, and the old files and folders have disappeared. I run Avast Free, and have scanned with MalwareBytes, HouseCall, Avast boot-time scan, and Avast full scan, in both normal and safe modes, but they find no problems. The same problem has appeared on my desktop and 2 laptops, all running Windows 7 Home premium 64 bit. I have attached a screen shot of one directory. I have NOT tried opening any of the files!
The only apparent problems I am having are occasional keyboard/mouse freeze and sporadic hang at shutdown, but these have been going on for years and I have no idea if they are related to the mystery files. Thanks for any help.

Thanks Callender, you nailed it - Cybereason RansomFree. I deleted it and the files disappeared, reinstalled and the files came back.