Which way is the best for clearing an harddisk?
What do you mean by clearing?
If you just want it empty, do a quick format. In the command prompt write: "format [drive letter]: /q"
If you want to erase the data so it's harder for someone to recover it, do "format [drive letter]:"
Hope it helps...
If you're selling or dumping the drive then secure-wipe it.
If not, just format.
There isn't a bargepole long enough for me to work on [a Sony Viao] - clocker 2008
well, I am just researching which one is the hardest way to recover files
Whenever I do a clean installation of an OS, I habitually erase the entire drive with Active Killdisk Hard Drive Eraser (the free version, of course). I just do a 'one-pass zero' erase, where the program just changes every bite to a zero. I'm an amateur, so given my limited knowledge of technology i think this is good enough.
You can download the .iso of Active Killdisk here if you are interested.