My hard disk drive(500GB) had two partitions and both were filled with images, software applications etc. Mistakenly I deleted around 70% present of data in my hdd and later I stored data again exclude previous data which means data which were stored before deleted them in hdd. Few month later I used recovery software and recovering my hdd again. Here I used trial version of that application, because of this reason it allows only to visible recovered data. That time my hdd was filled around 400GB(after deleted data from the hdd) and recovery application gave me around 150GB data correctly and rest of the data were crashed. My hdd size was 500GB though it only showed 467GB and how recovery application kept another 150GB . how those data come from even I did not use internet connection. Can someone explain this ?

I searched about this through internet and it said this couldn’t be happen. but I had experienced about this and I want to know whether are there any experience persons about this.