Copy Paste Problem

I copy my pictures in my hardrive and paste it again. Usually windows will prompt to overwrite or not. But, it paste the files with the name of copy. I cannot solve this problem. I want the windows to ask whether want to overwrite or not. Please give any suggestions.

If you are finding that the pictures are being pasted with the name "copy of xx", that is indicative of sloppy mouse work. You have moved the mouse while copying the picture and windows will automatically copy the picture (or pictures) in the same folder with the name as above. Hope this helps.

Or he checked the box to not notify him again when he's copying duplicates. Which if he did, don't know how to enable the prompt again.

I think Johnb35 said was right. How to enable it? It would be useful for me.