put file from Mac to Win

Hi
I got the problem that I can't push the file from desktop of the Mac to a folder in the Windows System. I have to take the file in the Windows Desktop to put it in a folder.
I don't know what happen that it doesn't work anymore.
Also I don't want all the files from the PC-Desktop on my Mac-Desktop. Also this feature has all of a sudden gone.
Does somebody know the problem?

Thanks a lot for your help!