Is my hard drive completely cleared when I use my master disc, or can previous infomation still be obtained?

Answer 1

It can be obtained using the appropriate recovery software.I would use software that uses the Guttman method which is a government standard for obliterating information from your hard drive.It is time consuming but it will permanently destroy everything without the worry that someone can recover your stuff.

Answer 2

If you mean by installing the operating from scrach, yes it will be. Just make sure you use a full install and that any other drives are also cleaned out.