Hi Kalaki
They well be right, normally this can be something like a media player, music match etc, in fact any program that indexes the files can cause it .
Obviously if that program says its using them, windows will not allow any other programs access, often the only cure is to turn of the program using it in the systray, or find a setting to untick to stop file cacheing or indexing.
Alternatively, try making a new incoming folder in
Settings -
File Transfers (in the left box ) then top right
Incoming File Folder to change the file you use, just make a new folder and browse for it .