Securely format a hard drive
I need to wipe my HDD before selling the PC. What is the best tool for it? It also would be great if it could run by booting from CD or Flash drive
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Darik's Boot and Nuke ("DBAN") is a self-contained boot disk that securely wipes the hard disks of most computers.
DBAN is free and open source software.
One can use the Linux dd command:
if you know what your doing... especially if you have other disks on the machine with data you want to keep on them. Make sure to get the right disk (the /dev/hda part). That being said, it's not all that hard to grab a Linux LiveCD (DSL is under 50 MB) and type it into a terminal. See also this thread at LinuxQuestions.org.
The most secure wiper is fire ;)
But if you use ANY tool that overwrites it lots of time (33 times is the most I've seen, called Guttman IIRC) then there's no way to recover anything even with government technology.
Also, it's very expensive to recover data. Something like $300 per GB here where I live, and up to 7 re-writes at most.