Please help im selling a used pc on ebay and i need to delete personal data for free.
My advise to you having been a free lance contractor for intelligence agencies, is that you remove your HDD, and sell him the PC, without the HDD. Not all that much money for the buyer to purchase his on HDD. (He should understand, your privacy concerns).
No matter what any software companies tell you that they can clean your HDD, drive of all data, this is not true, even if they use bleech, gutman technique, with many write overs, etc. etc. Still any good forensic computer expert can strip the data off your HDD.
Not even a reformat will prevent any good computer expert from stripping the data off your HDD. All of the answers saying “Reformat”, is 100% wrong.
The only way to prevent a forensic expert from stripping data off your HDD, is to beat with a hammer, then it is impossible, or remove the HDD. If you remove, don’t throw in the garbage safe in your home safe or other safe place.