Windows 7: Solo and no homegroup yet locks spontaneously appear on folders

I hope this is the right section to ask this question. I'm a solo flyer on this computer and I don't think I created a homegroup when I had to reset to factory settings a month or so ago. Yet locks appeared on my photo folders mysteriously. This concerned me because little things like this preceded the last crash.

I selected all the affected folders and right-clicked. Then I clicked on the lock where it said "share: nobody" to see what would happen (if anything) and all the locks disappeared. So that's fine but I'd like to know what caused something like this to spontaneously happen.

The only thing I've done recently is delete a ton of photos I've decided I probably won't ever print. I went from 950gb down to 520 in a short period of time.

-confused...