A friend of mine want me to wipe his hard drive completely and he is willing to pay me so i would like to know what i need to do it and how much should i charge him
internal i believe and would it be possible to clear it all by formatting it and if so what should i format it in
You can format it. Just hook it up to your computer and ensure that your computer boots up onto your own harddrive. If it boots into the other one, just change the boot order. You should format it to NTFS for maximum transfer speed and reliability.
A reformat doesn't 'Wipe'. A DBAN re-writes over all files with random numbers. Basically, making anything unrecoverable.
10-20 dollars should suffice. He doesn't want a reformat, and only a wiped drive. So go to: http://www.dban.org/ Here you'll be told exactly what to do, but it's as simple and burning to a disc, booting up the PC and removing everything. Read up on the site, though, if you're really unsure.