A couple clarifying questions that might help someone better help you:

1. What operation system and version are you running? (for example: Windows 7, Windows 10, other)
2. Are you attempting to rename a file in a local folder or a shared network folder?

Something you may, or may not be be interested in reading while waiting on someone
more qualified to come along:
Error renaming files in a shared folder - invalid filename error but no invalid characters (I realize that's an old thread but that doesn't mean it's not still useful)

Thanks for responding, Chuggerguy. It is not a shared folder, my personal folder of pictures. Some of the pictures have been downloaded from Facebook. I am going to read the link you provided.

I am running Windows 10 Professional (x64) Version 1803 (build 17134.191). Hope this info helps.

Thanks, Elmer. That is exactly what I was doing when trying to rename the pictures, but would always get the above Rename pop up. Think I will wait a few days and try it again.

As a test, can you copy one to your desktop, rename it there, and then copy it back?

If so, maybe it's the path name Explorer is having the problem with, rather than the file name itself.

Its possible you have a space in the file name. Delete all of the text, and use your right arrow and go as far right as possible to make sure you’re at the end of the name, then delete away. Then give it a name of 1 or test or whatever, something simple to see if that works.

Interestingly, after the most recent upfdate for Windows Insiders Windows 10 for people in the slow lane, I tried renaming the photographs again, and it now allowing me to do that. Thanks to all of you for your advice.