In general, there are two kind of data erasure software.
One is to erase hard disc including OS. This case, you need to boot from CD or USB memory (newer PC). Our Perfect Easy Eraser does complete HDD erasure including OS and clip area.
Another is to run on OS and erase files, folders and free space. Black Hole X4 runs on Windows OS including Win 7 and does complete data erasure of files/folders/free space. Our program is patented in Japan.