How to lock (pword) a folder? -not every single files inside, but the folder itself? ?

i learned from other questions but many of the answers given were about to merely put pword on every single files in a folder (archive). what i want is how to put pword on the folder itself SO THAT nobody can even know what the files lie inside... if the only way is to use certain software, plz suggest me a good one.. freeware will b better... thnx.