my problem is with the calculation of free memory in one of my disc's viz., D

        the attached image can explain u more than i can tell you

          anyway the problem is everything from Properties window to Everest application shows me the free memory available is something near to 1.5GB but when i select all the folders and files(hidden files is not included here) in the disc D and then rightclick-> properties, it shows to be occupying 5.35 GB (and if hidden files included it comes to around 5.55 GB) and thus my doubt arises here

            total disc space = 10     GB
            used space        =  5.35 GB
             therefore
             free space         = 10 - 5.35 = 3.99GB not equal to 1.5 GB as showed by everything including Everest application!!!!!!!!!!!!!!!!!!!

              what may be the problem????????

               am i wrong in calculation????

               or something crappy inside my disc???????????
           

disk cleanup or ccleaner, defrag, then try again?