Download http
/dban.org/ to USB
Follow directions.
I would first use Ccleaner to wipe and overwrite the entire disk using the Gutmann(35 times overwrite) option. DBAN isn't as thorough.
We've no clue WHY you want to do this. Selling PC. New OS. Reformatting. etc..
We don't know if this is the only disk.
The second option is more secure. Depends on your needs.
We don't know if it is a SSD or HDD. DBAN can't see SSDs.
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