So occasionally I'm working on something, then I save and close it, and there's this weird file. If the image is called Panda(.png) then there will be a PDNBAK file called Panda.png.0.pdnBak, I don't know what it is but judging by the "BAK" thing, it may be a backup, which I don't need since I just saved and closed the file. I can't open it or delete it (the bak file; the normal one works fine), and it's just sitting there. It doesn't seem to affect anything, but my folders are crowded enough and it's really annoying.
Also, I had this problem before once and it was fixed, but I don't remember how.
Any help is appreciated!