Rename .mp4 files without having them played in viewer

Whenever I try to rename a file - especially video clips/files - DOp 10 will not permit me to do so because it claims that the file is active.
I just highlight the file to be renamed and it immediately plays preventing me from changing its name.
I checked in Preferences and the forum but am not able to find an answer to my problem. Is there any hope for me?
Thank you very much for any suggestions.

I only turn on the viewer when I actually want to view things.

If you want the viewer on all the time, open Preferences and configure the ActiveX plugin, then enable the Windows Media Player preview handler, which requires you to click in the viewer to start music and video files playing. (You'll also need to turn off the Movie plugin back in Preferences.) But I'm not sure what the point of having the viewer on is in that case, since you can toggle the viewer itself via a single click and that seems more convenient,a least to me, than having to click xtra times every time you do want to play a file.

Leo,
Thanks for your quick reply which helped me figure our how to rename the video files without having them played.
As you suggested, I turn the Viewer off and then select the file to be renamed with an "Arrow" key only.
If I use the mouse to select the file, Media Player will open immediately in its own pop-up and play the file.
Thank you very much for your help and suggestions.

If media player opens on single-click, you must have turned on single-click ("point to select") mode.

Leo,

Yes, indeed I had this turned on.
After a long search of where this option is located, I now turned it off and now it works like a charm.
Again, many thanks for your extremely speedy help.