Wipe unallocated space completely
No matter you format or delete the partition, you can't clear up the data on the unallocated space completely. In this condition, you should think use Partition Assistant Server Edition to achieve it.
Step1: Launch Partition Assistant Server, right click and select "Advanced" >"Wipe Data".
Step2. In the pop-up window, you can manually enter the number of Over-writing passes between 1 and 100.
Step3. Click "Apply". You can check what operations you have already done in the "Pending Operations" panel.
A pending operations dialog box will pop up. You can see the detail operations. Click "Proceed
" to start wiping unallocated space.
With the help of Partition Assistant Server Edition, you can easily wipe the data of unallocated partition. free download it and try.