follow the steps.
1.Right click on the desktop or any place(your choice).
2.create a new folder
3.Now rename the folder with a space(you have to hold ALT key and type 0160).
4.Now you have a folder without a name.
5.just move your secret file to this folder.
6.Right click on the folder and select properties then select customize => Click on change icon.
7.Scroll a bit, you should find some empty spaces, Click on any one of them.then click ok.
That's all now your folder was invisible.if you want visible the same folder just rename the folder and change icon(same methods)
if this trick are useful then share and leave a comment.